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-rw-r--r--contrib/chem/examples/122/README.txt57
-rw-r--r--contrib/chem/examples/122/ch2a_ethyl.chem43
-rw-r--r--contrib/chem/examples/122/ch2b_benzene.chem38
-rw-r--r--contrib/chem/examples/122/ch2c_benzene_right.chem36
-rw-r--r--contrib/chem/examples/122/ch4a_stick.chem45
-rw-r--r--contrib/chem/examples/122/ch4b_methyl_acetate.chem47
-rw-r--r--contrib/chem/examples/122/ch4c_colon.chem42
-rw-r--r--contrib/chem/examples/122/ch4d_HCl.H2O.chem38
-rw-r--r--contrib/chem/examples/122/ch4e_CaSO4.2H2O.chem38
-rw-r--r--contrib/chem/examples/122/ch4f_C.chem48
-rw-r--r--contrib/chem/examples/122/ch4g_BP.chem48
-rw-r--r--contrib/chem/examples/122/ch4h_methacrylate.chem65
-rw-r--r--contrib/chem/examples/122/ch4i_cyclo.chem45
-rw-r--r--contrib/chem/examples/122/ch4j_ring4.chem40
-rw-r--r--contrib/chem/examples/122/ch4k_ring3.chem40
-rw-r--r--contrib/chem/examples/122/ch4l_vertex.chem45
-rw-r--r--contrib/chem/examples/122/ch4m_double.chem38
-rw-r--r--contrib/chem/examples/122/ch4n_triple.chem38
-rw-r--r--contrib/chem/examples/122/ch4o_aromatic.chem37
-rw-r--r--contrib/chem/examples/122/ch4p_cholestanol.chem60
-rw-r--r--contrib/chem/examples/122/ch4q_rings.chem46
-rw-r--r--contrib/chem/examples/122/ch4r_spiro.chem42
-rw-r--r--contrib/chem/examples/122/ch4s_heteroatoms.chem38
-rw-r--r--contrib/chem/examples/122/ch4t_polycyclic.chem49
-rw-r--r--contrib/chem/examples/122/ch4u_nicotine.chem42
-rw-r--r--contrib/chem/examples/122/ch4v_histidine.chem44
-rw-r--r--contrib/chem/examples/122/ch4w_lsd.chem50
-rw-r--r--contrib/chem/examples/122/ch4x_anisole.chem42
-rw-r--r--contrib/chem/examples/122/ch4y_reserpine.chem62
-rw-r--r--contrib/chem/examples/122/ch4z1_eqn_glutamic.chem78
-rw-r--r--contrib/chem/examples/122/ch4z2_text.chem53
-rw-r--r--contrib/chem/examples/122/ch5a_size.chem45
-rw-r--r--contrib/chem/examples/122/ch6a_pic.chem43
-rw-r--r--contrib/chem/examples/122/ch6b_dna.chem59
-rw-r--r--contrib/chem/examples/122/chAa_polymer.chem72
-rw-r--r--contrib/chem/examples/122/chAb_vinyl_chloro.chem62
-rw-r--r--contrib/chem/examples/122/chAc_morphine.chem52
-rw-r--r--contrib/chem/examples/122/chAd_chlorophyll.chem69
-rw-r--r--contrib/chem/examples/122/chAe_chair.chem49
-rw-r--r--contrib/chem/examples/122/chAf_arrow.chem68
-rw-r--r--contrib/chem/examples/122/chAg_circle.chem54
-rw-r--r--contrib/chem/examples/122/chAh_brackets.chem60
-rw-r--r--contrib/chem/examples/122/chAi_poly_vinyl_chloride.chem141
-rw-r--r--contrib/chem/examples/122/chBa_jump.chem41
-rw-r--r--contrib/chem/examples/122/chBb_bonds.chem42
-rw-r--r--contrib/chem/examples/122/chBc_rings.chem43
-rw-r--r--contrib/chem/examples/README.txt47
-rw-r--r--contrib/chem/examples/atp.chem58
-rw-r--r--contrib/chem/examples/cholesterin.chem47
-rw-r--r--contrib/chem/examples/ethamivan.chem43
-rw-r--r--contrib/chem/examples/lsd.chem46
-rw-r--r--contrib/chem/examples/morphine.chem51
-rw-r--r--contrib/chem/examples/penicillin.chem52
-rw-r--r--contrib/chem/examples/reserpine.chem63
54 files changed, 2741 insertions, 0 deletions
diff --git a/contrib/chem/examples/122/README.txt b/contrib/chem/examples/122/README.txt
new file mode 100644
index 0000000..6f3809b
--- /dev/null
+++ b/contrib/chem/examples/122/README.txt
@@ -0,0 +1,57 @@
+This directory contains the examples for the 'chem' language written
+in the book:
+
+ Computing Science Technical Report No. 122
+ CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+ by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+
+The book is available in the internet at
+<http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+Many of the examples had to be fixed. Unfortunately, the 'chem' akw
+version does not run on many of these programs. But the Perl version
+of 'chem' works on all examples.
+
+Most examples do not use the modern chemical display. They have C
+atoms added, whereas the modern method omits all C atoms and their
+directly appended H atoms.
+
+The examples are named and sorted by the chapter where they are found
+in the book. For example, the file 'ch4c_colon.chem' means a 'chem'
+example in chapter 4; according to 'c', it is the third example in
+this chapter; the name 'colon' is used to describe the context of the
+example.
+
+You can view the graphical display of the examples by calling
+
+ @g@chem <file> | groff -p ...
+
+
+####### License
+
+Copyright (C) 2006-2020 Free Software Foundation, Inc.
+Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+This file is part of 'chem', which is part of 'groff'.
+
+'groff' is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License (GPL) version 2 as
+published by the Free Software Foundation.
+
+'groff' is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+The GPL2 license text is available in the internet at
+<http://www.gnu.org/licenses/gpl-2.0.html>.
+
+
+##### Editor settings
+
+Local Variables:
+mode: text
+End:
diff --git a/contrib/chem/examples/122/ch2a_ethyl.chem b/contrib/chem/examples/122/ch2a_ethyl.chem
new file mode 100644
index 0000000..089de73
--- /dev/null
+++ b/contrib/chem/examples/122/ch2a_ethyl.chem
@@ -0,0 +1,43 @@
+ch2a_ethyl.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ CH3
+ bond
+ CH2
+ bond
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+.cend
diff --git a/contrib/chem/examples/122/ch2b_benzene.chem b/contrib/chem/examples/122/ch2b_benzene.chem
new file mode 100644
index 0000000..0af1c9f
--- /dev/null
+++ b/contrib/chem/examples/122/ch2b_benzene.chem
@@ -0,0 +1,38 @@
+ch2b_benzene.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ benzene
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch2c_benzene_right.chem b/contrib/chem/examples/122/ch2c_benzene_right.chem
new file mode 100644
index 0000000..d9f29b5
--- /dev/null
+++ b/contrib/chem/examples/122/ch2c_benzene_right.chem
@@ -0,0 +1,36 @@
+ch2c_benzene_right.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ benzene pointing right # a rotated benzene ring
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4a_stick.chem b/contrib/chem/examples/122/ch4a_stick.chem
new file mode 100644
index 0000000..f4caef3
--- /dev/null
+++ b/contrib/chem/examples/122/ch4a_stick.chem
@@ -0,0 +1,45 @@
+ch4a_stick.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ bond right
+ bond 60
+ bond 120
+ bond 60
+ bond 120
+ bond down
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+.cend
diff --git a/contrib/chem/examples/122/ch4b_methyl_acetate.chem b/contrib/chem/examples/122/ch4b_methyl_acetate.chem
new file mode 100644
index 0000000..31625a3
--- /dev/null
+++ b/contrib/chem/examples/122/ch4b_methyl_acetate.chem
@@ -0,0 +1,47 @@
+ch4b_methyl_acetate.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+CH3 # the 3 is automatically turned into a subscript
+bond # the implicit direction is right
+ # implicit connection is to right side of CH3
+C
+double bond 30 # by default, from the substituent C
+O
+bond 120 from C # must be "from C"; otherwise would leave from O
+O
+bond right
+CH3
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4c_colon.chem b/contrib/chem/examples/122/ch4c_colon.chem
new file mode 100644
index 0000000..5e42f6b
--- /dev/null
+++ b/contrib/chem/examples/122/ch4c_colon.chem
@@ -0,0 +1,42 @@
+ch4c_colon.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ CH3
+ bond ; C
+ double bond 30 ; O
+ bond 120 from C ; O
+ bond right ; CH3
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4d_HCl.H2O.chem b/contrib/chem/examples/122/ch4d_HCl.H2O.chem
new file mode 100644
index 0000000..b6ac99d
--- /dev/null
+++ b/contrib/chem/examples/122/ch4d_HCl.H2O.chem
@@ -0,0 +1,38 @@
+ch4d_HCl.H2O.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ HCl.H2O
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4e_CaSO4.2H2O.chem b/contrib/chem/examples/122/ch4e_CaSO4.2H2O.chem
new file mode 100644
index 0000000..b2f8bc0
--- /dev/null
+++ b/contrib/chem/examples/122/ch4e_CaSO4.2H2O.chem
@@ -0,0 +1,38 @@
+ch4e_CaSO4.2H2O.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ CaSO4.2H2O
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4f_C.chem b/contrib/chem/examples/122/ch4f_C.chem
new file mode 100644
index 0000000..d54461f
--- /dev/null
+++ b/contrib/chem/examples/122/ch4f_C.chem
@@ -0,0 +1,48 @@
+ch4f_C.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ bond ; C # 1st definition of C
+ bond up from C
+ bond down from C
+ bond right from C ; C # 2nd definition of C
+ bond up from C
+ bond down from C
+ bond right from C ; C # 3rd definition of C
+ bond up from C
+ bond down from C
+ bond right from C
+
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4g_BP.chem b/contrib/chem/examples/122/ch4g_BP.chem
new file mode 100644
index 0000000..9c6af4b
--- /dev/null
+++ b/contrib/chem/examples/122/ch4g_BP.chem
@@ -0,0 +1,48 @@
+ch4g_BP.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+# this is the isopropyl group
+ bond 120 ; BP # BP is right end of this bond
+ bond -120 from BP
+ bond right from BP ; C
+ front bond up ; CH3
+ back bond down from C ; D
+ bond right from C ; BP
+# redefine BP to mean the center carbon of this t-butyl group
+ bond up from BP
+ bond right from BP
+ bond down from BP
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4h_methacrylate.chem b/contrib/chem/examples/122/ch4h_methacrylate.chem
new file mode 100644
index 0000000..8300d25
--- /dev/null
+++ b/contrib/chem/examples/122/ch4h_methacrylate.chem
@@ -0,0 +1,65 @@
+ch4h_methacrylate.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ bond dotted
+ bond right ; BP
+ bond up from BP ; C
+ double bond -60 from C ; O
+ bond 60 length .1 from C ; OCH3
+ bond down from BP ; CH3
+# begin second segment of polymer
+ bond right length .5 from BP ; BP
+ bond up length .1 from BP ; H
+ bond down length .1 from BP ; H
+# begin third segment of polymer
+ bond right length .5 from BP ; BP
+ bond up from BP ; C
+ double bond -60 from C ; O
+ bond 60 length .1 from C ; OCH3
+ bond down from BP ; CH3
+# begin fourth segment of polymer
+ bond right length .5 from BP ; BP
+ bond up length .1 from BP ; H
+ bond down length .1 from BP ; H
+# begin fifth segment of polymer
+ bond right length .5 from BP ; BP
+ bond up from BP ; C
+ double bond -60 from C ; O
+ bond 60 length .1 from C ; OCH3
+ bond down from BP ; CH3
+ bond right from BP
+ bond dotted
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4i_cyclo.chem b/contrib/chem/examples/122/ch4i_cyclo.chem
new file mode 100644
index 0000000..866e6f7
--- /dev/null
+++ b/contrib/chem/examples/122/ch4i_cyclo.chem
@@ -0,0 +1,45 @@
+ch4i_cyclo.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R3: ring3
+R4: ring4 at R3 + (.75,0)
+R5: ring5 at R4 + (.75,0)
+R6: ring6 at R5 + (.75,0)
+B: benzene at R6 + (.75,0)
+R7: ring7 at B + (.75,0)
+R8: ring8 at R7 + (.75,0)
+
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4j_ring4.chem b/contrib/chem/examples/122/ch4j_ring4.chem
new file mode 100644
index 0000000..9caf718
--- /dev/null
+++ b/contrib/chem/examples/122/ch4j_ring4.chem
@@ -0,0 +1,40 @@
+ch4j_ring4.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ ring4 pointing 45
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+.cend
diff --git a/contrib/chem/examples/122/ch4k_ring3.chem b/contrib/chem/examples/122/ch4k_ring3.chem
new file mode 100644
index 0000000..2a2d856
--- /dev/null
+++ b/contrib/chem/examples/122/ch4k_ring3.chem
@@ -0,0 +1,40 @@
+ch4k_ring3.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R: ring3
+ back bond 120 from R.V2 ; C2H5
+ front bond -120 from R.V3 ; HO
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4l_vertex.chem b/contrib/chem/examples/122/ch4l_vertex.chem
new file mode 100644
index 0000000..d9fcb07
--- /dev/null
+++ b/contrib/chem/examples/122/ch4l_vertex.chem
@@ -0,0 +1,45 @@
+ch4l_vertex.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R: benzene pointing right
+ bond left from R.V4 ; HO
+ bond -150 from R.V3 ; CH3O
+ bond right from R.V1 ; C
+ double bond up from C ; O
+ bond right from C ; N
+ bond 45 ; C2H5
+ bond 135 from N ; C2H5
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4m_double.chem b/contrib/chem/examples/122/ch4m_double.chem
new file mode 100644
index 0000000..c5b1373
--- /dev/null
+++ b/contrib/chem/examples/122/ch4m_double.chem
@@ -0,0 +1,38 @@
+ch4m_double.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ ring double 1,2 3,4 5,6
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4n_triple.chem b/contrib/chem/examples/122/ch4n_triple.chem
new file mode 100644
index 0000000..5766f85
--- /dev/null
+++ b/contrib/chem/examples/122/ch4n_triple.chem
@@ -0,0 +1,38 @@
+ch4n_triple.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ ring8 triple 3,4
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4o_aromatic.chem b/contrib/chem/examples/122/ch4o_aromatic.chem
new file mode 100644
index 0000000..aa303c7
--- /dev/null
+++ b/contrib/chem/examples/122/ch4o_aromatic.chem
@@ -0,0 +1,37 @@
+ch4o_aromatic.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R: aromatic ring7
+ "+" at R
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4p_cholestanol.chem b/contrib/chem/examples/122/ch4p_cholestanol.chem
new file mode 100644
index 0000000..e292bea
--- /dev/null
+++ b/contrib/chem/examples/122/ch4p_cholestanol.chem
@@ -0,0 +1,60 @@
+ch4p_cholestanol.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R1: ring6
+ "R1" at R1 # this puts a label at R1
+ front bond -120 from R1.V5 ; HO
+ # the following line says "fuse the next six-
+ # membered ring with its 6th vertex joining
+ # the second vertex of R1"
+R2: ring6 with .V6 at R1.V2
+ front bond up from R2.V6 ; CH3
+ back bond down from R2.V4 ; H
+ back bond down from R2.V1 ; H
+ front bond up from R2.V2 ; H
+R3: ring6 with .V4 at R2.V2
+R4: flatring with .V5 at R3.V2
+ front bond up from R4.V5 ; CH3
+ back bond down from R4.V4 ; H # this is the alkyl chain
+ bond up from R4.V1 ; BP
+ bond -60 from BP
+ bond 60 from BP
+ bond 120
+ bond 60
+ bond 120 ; BP
+ bond down from BP
+ bond 60 from BP
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4q_rings.chem b/contrib/chem/examples/122/ch4q_rings.chem
new file mode 100644
index 0000000..bafdd92
--- /dev/null
+++ b/contrib/chem/examples/122/ch4q_rings.chem
@@ -0,0 +1,46 @@
+ch4q_rings.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R3: ring3
+R4: ring4 pointing 45 with .V1 at R3.V2
+R5: ring5 pointing down with .V4 at R4.V2
+R6: ring6 pointing 54 with .V6 at R5.V5
+ # the following lines specify the labels inside the rings
+ "3" at R3
+ "4" at R4
+ "5" at R5
+ "6" at R6
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4r_spiro.chem b/contrib/chem/examples/122/ch4r_spiro.chem
new file mode 100644
index 0000000..24ec050
--- /dev/null
+++ b/contrib/chem/examples/122/ch4r_spiro.chem
@@ -0,0 +1,42 @@
+ch4r_spiro.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R1: ring6
+R2: ring6 with .V1 at R1.V4
+R3: ring5 with .V5 at R2.V3
+ back bond 60 from R3.V2 ; OH
+ front bond 150 from R3.V3 ; OH
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4s_heteroatoms.chem b/contrib/chem/examples/122/ch4s_heteroatoms.chem
new file mode 100644
index 0000000..7dc8ba7
--- /dev/null
+++ b/contrib/chem/examples/122/ch4s_heteroatoms.chem
@@ -0,0 +1,38 @@
+ch4s_heteroatoms.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ ring put N at 2 put S at 4 double 2,3 4,5 6,1
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4t_polycyclic.chem b/contrib/chem/examples/122/ch4t_polycyclic.chem
new file mode 100644
index 0000000..fc6b580
--- /dev/null
+++ b/contrib/chem/examples/122/ch4t_polycyclic.chem
@@ -0,0 +1,49 @@
+ch4t_polycyclic.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R1: benzene pointing right
+ bond 30 from R1.V6 ; Br
+R2: benzene pointing right with .V5 at R1.V1
+R3: benzene pointing right with .V1 at R2.V3
+ bond 150 from R3.V2 ; CO2H
+R4: benzene pointing right with .V1 at R1.V3
+# next line names bond B1 so we can refer to its end
+B1: bond left from R4.V4
+ ring6 put N at 4 double 2,3 4,5 6,1 with .V3 at B1.end
+B2: bond right from R2.V1
+R5: benzene with .V5 at B2.end
+ ring6 put N at 4 double 1,2 3,4 with .V5 at R5.V3
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4u_nicotine.chem b/contrib/chem/examples/122/ch4u_nicotine.chem
new file mode 100644
index 0000000..d38a7c8
--- /dev/null
+++ b/contrib/chem/examples/122/ch4u_nicotine.chem
@@ -0,0 +1,42 @@
+ch4u_nicotine.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ benzene put N at 4
+ bond right
+ ring5 pointing down put N at 1
+ bond down from .N ; CH3 # or .V1
+
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4v_histidine.chem b/contrib/chem/examples/122/ch4v_histidine.chem
new file mode 100644
index 0000000..33a4e9d
--- /dev/null
+++ b/contrib/chem/examples/122/ch4v_histidine.chem
@@ -0,0 +1,44 @@
+ch4v_histidine.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R1: flatring pointing down put N at 2 put N at 5 double 1,2 3,4
+ H right of R1.V5
+ bond right from R1.V4 ; CH2
+ bond right ; C
+ bond up from C ; H
+ bond down from C ; NH2
+ bond right from C ; CO2H
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4w_lsd.chem b/contrib/chem/examples/122/ch4w_lsd.chem
new file mode 100644
index 0000000..aa68b00
--- /dev/null
+++ b/contrib/chem/examples/122/ch4w_lsd.chem
@@ -0,0 +1,50 @@
+ch4w_lsd.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+B: benzene pointing right
+F: flatring pointing left put N at 5 double 3,4 with .V1 at B.V2
+ H below F.N
+R: ring pointing right with .V4 at B.V6
+ front bond right from R.V6 ; H
+W: ring pointing right with .V2 at R.V6 put N at 1 double 3,4
+ bond right from W.N ; CH3
+ back bond -60 from W.V5 ; H
+ bond up from W.V5 ; C
+ double bond up from C ; O
+ bond right from C ; N
+ bond 45 from N ; C2H5
+ bond 135 from N ; C2H5
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4x_anisole.chem b/contrib/chem/examples/122/ch4x_anisole.chem
new file mode 100644
index 0000000..ec78417
--- /dev/null
+++ b/contrib/chem/examples/122/ch4x_anisole.chem
@@ -0,0 +1,42 @@
+ch4x_anisole.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R1: benzene
+ bond down from R1.V4 ; OCH3
+R2: benzene at R1 + (1.5,0)
+ bond down from R2.V4 ; O
+ CH3 right of O
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4y_reserpine.chem b/contrib/chem/examples/122/ch4y_reserpine.chem
new file mode 100644
index 0000000..fb5d1ca
--- /dev/null
+++ b/contrib/chem/examples/122/ch4y_reserpine.chem
@@ -0,0 +1,62 @@
+ch4y_reserpine.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+# Some corrections were added.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ CH3O
+ bond 60
+R1: benzene
+R2: aromatic flatring5 pointing down put N at 1 with .V3 at R1.V2
+ H below R2.V1
+R3: ring put N at 3 with .V5 at R2.V5
+R4: ring put N at 1 with .V1 at R3.V3
+ back bond -120 from R4.V4 ; H
+ back bond 60 from R4.V3 ; H
+R5: ring with .V1 at R4.V3
+ bond -120 ; C
+ double bond down from C ; O
+ CH3O left of C
+ back bond 60 from R5.V3 ; H
+ back bond down from R5.V4 ; O
+ CH3 right of O
+ bond 120 from R5.V3 ; O
+ bond right length .1 from O ; C
+ double bond down ; O
+ bond right length .1 from C
+B: benzene pointing right
+ bond 30 from B.V6 ; OCH3
+ bond right from B.V1 ; OCH3
+ bond 150 from B.V2 ; OCH3
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch4z1_eqn_glutamic.chem b/contrib/chem/examples/122/ch4z1_eqn_glutamic.chem
new file mode 100644
index 0000000..6cecd7c
--- /dev/null
+++ b/contrib/chem/examples/122/ch4z1_eqn_glutamic.chem
@@ -0,0 +1,78 @@
+ch4z1_eqn_glutamic.chem:
+.br
+.EQ
+delim $$
+.EN
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+# Some corrections were added.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+# a left bracket
+ bond right length .1 ; BP
+ bond up length .3
+ bond right length .1
+ bond down length .3 from BP
+ bond right length .1
+# this is the mainchain amide structure
+ bond right length .1 from BP ; NH
+ bond right ; CH
+# label the CH with an alpha, intended for eqn.
+# this line says "put the north edge of the alpha at the
+# south edge of the CH"
+ "$alpha$" with .n at CH.s
+ bond right from CH ; C
+ double bond up from C ; O
+ bond right length .1 from C ; BP
+# a right bracket
+ bond up length .3
+ bond left length .1
+ bond right length .1 from BP
+ bond down length .3 from BP ; BP
+ bond left length .1
+# label the degree of polymerization
+ "$n$" with .w at BP.se
+# this is the sidechain
+ bond up from CH ; CH2
+ "$beta$" with .e at CH2.w
+ bond up from CH2 ; CH2
+ "$gamma$" with .e at CH2.w
+ bond up from CH2 ; C
+# this is the benzyl ester part
+ double bond -60 from C ; O
+ bond 60 from C ; O
+ bond right ; CH2C6H5
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
+.EQ
+delim off
+.EN
diff --git a/contrib/chem/examples/122/ch4z2_text.chem b/contrib/chem/examples/122/ch4z2_text.chem
new file mode 100644
index 0000000..2000636
--- /dev/null
+++ b/contrib/chem/examples/122/ch4z2_text.chem
@@ -0,0 +1,53 @@
+ch4z2_text.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ bond 120 dotted
+ bond 120 length .3 ; BP
+ back bond -120 length .25 from BP ; H
+ front bond 120 length .25 from BP ; CH3
+ bond 60 length .5 from BP ; BP
+ bond -60 length .25 from BP ; H
+# note the pic move command to position the text
+ move left .35 ; "(ANTI)"
+ front bond 60 length .25 from BP ; H
+# another positioning of text
+ move right .35 ; "(SYN)"
+ bond 120 length .4 from BP ; BP
+ back bond -120 length .25 from BP ; H
+ front bond 120 length .25 from BP ; CH3
+ bond 60 length .5 from BP
+ bond 60 dotted
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch5a_size.chem b/contrib/chem/examples/122/ch5a_size.chem
new file mode 100644
index 0000000..d4eb33f
--- /dev/null
+++ b/contrib/chem/examples/122/ch5a_size.chem
@@ -0,0 +1,45 @@
+ch5a_size.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+.ps 14
+size 16
+R: ring6 put O at 1 put C at 2 put O at 3 put C at 4 put O at 5 put C at 6
+ double bond 60 from R.V2 ; NH
+ double bond down from R.V4 ; NH
+ double bond -60 from R.V6 ; HN
+size 10 # if you are doing more than one
+.ps 10
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch6a_pic.chem b/contrib/chem/examples/122/ch6a_pic.chem
new file mode 100644
index 0000000..ad6dea6
--- /dev/null
+++ b/contrib/chem/examples/122/ch6a_pic.chem
@@ -0,0 +1,43 @@
+ch6a_pic.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R: ring double 2,3
+ line from R.V6 to R.C
+ line from R.C to R.V4
+ X1: 1/2 <R.V5,R.C>
+ X2: 1/2 <R.C,R.V2>
+ bond from X1 to X2
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/ch6b_dna.chem b/contrib/chem/examples/122/ch6b_dna.chem
new file mode 100644
index 0000000..00abbba
--- /dev/null
+++ b/contrib/chem/examples/122/ch6b_dna.chem
@@ -0,0 +1,59 @@
+ch6b_dna.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+P: [
+R1: flatring pointing up put N at 1 put N at 4 double 5,1
+ bond -135 from R1.V4 ; BP
+ "deoxyribose" rjust with .e at BP.w
+R2: ring6 put N at 2 put N at 4 double 1,2 3,4 5,6 with .V6 at R1.V2
+ pic Conn: R2.V2.ne #because naming is too restricted in pic
+ bond up from R2.V1 ; N
+ bond -60 from N ; H
+ bond 60 from N ; H
+]
+ # thymine
+Q: [
+R3: ring6 put N at 3 put N at 5 double 1,2
+ bond up from R3.V1 ; CH3
+ bond 120 from R3.V3 ; BP
+ "deoxyribose" ljust with .w at BP.e
+ double bond down from R3.V4 ; O
+ double bond -60 from R3.V6 ; O
+ bond -120 from R3.V5 ; H
+] with .O at P.H + (.3,.3)
+ bond from Q.O.sw to P.H.ne dotted
+ bond from Q.H.sw to P.Conn dotted
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chAa_polymer.chem b/contrib/chem/examples/122/chAa_polymer.chem
new file mode 100644
index 0000000..3293454
--- /dev/null
+++ b/contrib/chem/examples/122/chAa_polymer.chem
@@ -0,0 +1,72 @@
+chAa_polymer.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+# epoxy based on the m-phenyldiamine cured bisphenol-A
+ size 8
+ bond dotted
+ bond ; N
+ bond ; CH2
+ bond down from N
+R1: benzene
+ bond 120 length .1 from R1.V3 ; N
+ bond right length .1 from N
+ bond down length .1 from N
+# back to the CH2
+ bond right from CH2 ; CH
+ bond down from CH ; OH
+ bond right from CH ; CH2
+ bond right ; O
+ bond right
+ benzene pointing right
+ bond right ; C
+ bond up from C ; CH3
+ bond down from C ; CH3
+ bond right from C
+ benzene pointing right
+ bond right ; O
+ bond right from O ; CH2
+ bond right ; CH
+ bond down from CH ; OH
+ bond right from CH ; CH2
+ bond right ; N
+ bond right from N
+ bond dotted
+ bond down from N
+R2: benzene
+ bond 120 length .1 from R2.V3 ; N
+ bond right length .1 from N
+ bond down length .1 from N
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chAb_vinyl_chloro.chem b/contrib/chem/examples/122/chAb_vinyl_chloro.chem
new file mode 100644
index 0000000..dff97fc
--- /dev/null
+++ b/contrib/chem/examples/122/chAb_vinyl_chloro.chem
@@ -0,0 +1,62 @@
+chAb_vinyl_chloro.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ Cl
+ bond 120 length .25 ; BP
+ bond 60 length .25 from BP ; Cl
+B1: double bond down length .3 from BP
+ bond 120 length .35 ; BP
+# now comes the ring
+R1: ring6 double 1,2 3,4 5,6 with .V6 at BP
+ bond up length .1 from R1.V1 ; H
+ bond 60 length .1 from R1.V2 ; H
+ bond 120 from R1.V3 ; O
+ bond 60 from O ; C
+ double bond up from C ; O
+ bond 120 from C
+# continue decorating the ring
+ bond down length .1 from R1.V4 ; H
+ bond -120 length .1 from R1.V5 ; H
+# now go back and do the left hand ring
+ bond -120 length .35 from B1.end ; BP
+R2: ring6 double 1,2 3,4 5,6 with .V2 at BP
+ bond up length .1 from R2.V1 ; H
+ bond -60 length .1 from R2.V6 ; H
+ bond -120 from R2.V5 ; O
+ bond -60 from O
+ bond down length .1 from R2.V4 ; H
+ bond 120 length .1 from R2.V3 ; H
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chAc_morphine.chem b/contrib/chem/examples/122/chAc_morphine.chem
new file mode 100644
index 0000000..c9fbf10
--- /dev/null
+++ b/contrib/chem/examples/122/chAc_morphine.chem
@@ -0,0 +1,52 @@
+chAc_morphine.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R1: ring6 double 1,2
+ bond -60 from R1.V6 ; HO
+R2: ring6 with .V1 at R1.V3
+ bond 60 from R2.V2 ; N
+ bond right from N ; CH3
+R3: benzene with .V1 at R2.V5
+ bond -120 from R3.V5 ; HO
+# this is the furan ring
+ bond -135 length .33 from R1.V5 ; O
+ bond -45 length .33 from R3.V6
+# this is the odd ring
+ bond up length .1 from N ; BP
+B1: bond up length .33 from R1.V4
+ bond to BP
+
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chAd_chlorophyll.chem b/contrib/chem/examples/122/chAd_chlorophyll.chem
new file mode 100644
index 0000000..e2acb22
--- /dev/null
+++ b/contrib/chem/examples/122/chAd_chlorophyll.chem
@@ -0,0 +1,69 @@
+chAd_chlorophyll.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ Mg
+ bond 45 ; N
+R1: ring5 pointing up put N at 4 double 1,2 4,5 with .V4 at N
+ bond up from R1.V1 ; CH3
+ bond right from R1.V2 ; CH2CH3
+ bond 135 from Mg ; N
+R2: ring5 pointing down put N at 3 double 1,2 4,5 with .V3 at N
+ bond right from R2.V5 ; CH3
+ bond 225 from Mg ; N
+R3: ring5 pointing down put N at 4 double 3,4 with .V4 at N
+ bond -45 from Mg ; N
+R4: ring5 pointing up put N at 3 double 1,5 with .V3 at N
+ bond left from R4.V5 ; H3C
+ bond up from R4.V1 ; CH
+ double bond right length .1 from CH ; CH2
+ double bond 150 length .3 from R1.V3
+ bond to R2.V4
+R5: ring5 pointing 72 with .V5 at R2.V2
+ double bond 135 from R5.V2 ; O
+ bond down from R5.V3 ; C
+ double bond left length .1 from C ; O
+ bond down from C ; O
+ CH3 left of O
+ double bond -25 from R5.V4
+ bond down from R3.V1 ; CH2
+ CH2 left of CH2
+ bond left ; C
+ double bond -45 ; O
+ bond -135 from C ; C20H39O
+ bond left from R3.V2 ; H3C
+ double bond -150 length .3 from R4.V4
+ bond to R3.V3
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chAe_chair.chem b/contrib/chem/examples/122/chAe_chair.chem
new file mode 100644
index 0000000..27b046a
--- /dev/null
+++ b/contrib/chem/examples/122/chAe_chair.chem
@@ -0,0 +1,49 @@
+chAe_chair.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+pic define chair { [
+ V1: bond 120 length .25
+ V2: bond right length .35
+ V3: bond 150 length .35
+ V4: bond -60 length .25
+ V5: bond left length .35
+ V6: bond to V1.start
+pic ] }
+R1: chair
+R2: chair with .V1 at R1.V4.start
+bond 60 from R2.V4.start ; CH3
+bond down from R2.V4.start ; OH
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chAf_arrow.chem b/contrib/chem/examples/122/chAf_arrow.chem
new file mode 100644
index 0000000..f135ecb
--- /dev/null
+++ b/contrib/chem/examples/122/chAf_arrow.chem
@@ -0,0 +1,68 @@
+chAf_arrow.chem:
+.br
+.EQ
+delim $$
+.EN
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+ bond length .1 ; BP
+ bond up length .5
+ bond right
+ bond down length .5 from BP
+ bond right
+ bond right from BP ; C
+ double bond up ; O
+ bond right from C
+ benzene pointing right
+ bond right ; C
+ double bond up from C ; O
+ bond right from C ; O
+ bond right ; CH2
+# this is the statement to make the arrow
+ line <- from CH2.s down
+ move down .1 ; "0.085"
+ CH2CH2CH2 right of CH2
+ bond right ; O
+ bond right length .1 ; BP
+ bond up length .5 from BP
+ bond left
+ bond right length .1 from BP
+ bond down length .5 from BP ; BP
+ bond left
+ "$n$" with .w at BP.se
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
+.EQ
+delim off
+.EN
diff --git a/contrib/chem/examples/122/chAg_circle.chem b/contrib/chem/examples/122/chAg_circle.chem
new file mode 100644
index 0000000..576c926
--- /dev/null
+++ b/contrib/chem/examples/122/chAg_circle.chem
@@ -0,0 +1,54 @@
+chAg_circle.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+bond 120 ; C
+bond 60 ; C
+bond up ; Cl
+double bond 120 from C ; C
+bond 60 ; C
+bond 120 ; C
+bond 60 ; C
+bond up ; Cl
+double bond 120 from C ; C
+circle at C rad .08
+bond 60 from C ; C
+bond 120 ; C
+bond 60 ; C
+double bond 120 ; C
+bond down ; Cl
+bond 60 from C ; C
+bond 120
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chAh_brackets.chem b/contrib/chem/examples/122/chAh_brackets.chem
new file mode 100644
index 0000000..7605a38
--- /dev/null
+++ b/contrib/chem/examples/122/chAh_brackets.chem
@@ -0,0 +1,60 @@
+chAh_brackets.chem:
+.br
+.EQ
+delim $$
+.EN
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+[
+ bond right ; CH2
+ bond 120 ; (CH2)
+ "$nothing sub n$"
+ bond 60 ; .CH2
+]
+# now put the arrow in
+ move right .3
+ arrow .5
+ move right .3
+# begin second structure
+[
+ bond right ; CH.
+ bond 120 ; (CH2)
+ "$nothing sub n$"
+ bond 60 ; CH3
+]
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
+.EQ
+delim $$
+.EN
diff --git a/contrib/chem/examples/122/chAi_poly_vinyl_chloride.chem b/contrib/chem/examples/122/chAi_poly_vinyl_chloride.chem
new file mode 100644
index 0000000..e4539bb
--- /dev/null
+++ b/contrib/chem/examples/122/chAi_poly_vinyl_chloride.chem
@@ -0,0 +1,141 @@
+chAi_poly_vinyl_chloride.chem:
+.br
+.ps -2
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+db = .12
+cwid = .095
+A: [
+ bond dotted
+ bond right ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; C.
+ bond down ; Cl
+ bond right from C ; CH2
+ bond ; CH2
+ bond down ; Cl
+]
+" (6.13a)" ljust at A.e
+arrow down .5 from A.s
+[
+ CH2
+ double bond right ; CHCl
+] with .w at last arrow.c
+B: [
+ bond dotted
+ bond right ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; C
+ bond up ; Cl
+ bond down from C ; CH2
+ bond ; CH2Cl
+ bond right from C ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH
+ bond dotted
+] with .n at end of last arrow
+" (6.13b)" ljust at B.e
+C: [
+ bond dotted
+ bond right ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; C.
+ bond down ; Cl
+ bond right from C ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; CH2
+ bond down ; Cl
+] with .n at B.s - (0,.5)
+" (6.14a)" ljust at C.e
+arrow down .3 from C.s
+[
+ CH2
+ double bond right
+ CHCl
+] with .w at last arrow.s
+arrow down .3 from last arrow.s
+
+D: [
+ bond dotted
+ bond right ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; C
+ bond up ; Cl
+ bond down from C ; CH2
+ bond ; CHCl
+ bond ; CH2
+ bond ; CH2Cl
+ bond right from C ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH
+ bond dotted
+] with .n at last arrow.s
+" (6.14b)" ljust at D.e
+E: [
+ bond dotted
+ bond ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; CH
+ bond down ; Cl
+ bond right from CH ; CH2
+ bond ; CH
+ bond down ; Cl
+] with .e at B.w - (.5,0)
+
+arrow from E.ne to A.sw
+arrow from E.se to C.nw
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
+.ps +2
diff --git a/contrib/chem/examples/122/chBa_jump.chem b/contrib/chem/examples/122/chBa_jump.chem
new file mode 100644
index 0000000..cd40a3a
--- /dev/null
+++ b/contrib/chem/examples/122/chBa_jump.chem
@@ -0,0 +1,41 @@
+chBa_jump.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+SiO2 # name = SiO2
+move right 1
+CH3CH2NH2.HCl # name = CH3CH2NH2HCl
+
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chBb_bonds.chem b/contrib/chem/examples/122/chBb_bonds.chem
new file mode 100644
index 0000000..bc29895
--- /dev/null
+++ b/contrib/chem/examples/122/chBb_bonds.chem
@@ -0,0 +1,42 @@
+chBb_bonds.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+C
+frontbond -170 from C ; H
+backbond 10 from C ; CO2H
+bond left length .15 from C ; H2N
+bond right from C ; CH3
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/122/chBc_rings.chem b/contrib/chem/examples/122/chBc_rings.chem
new file mode 100644
index 0000000..950cd0b
--- /dev/null
+++ b/contrib/chem/examples/122/chBc_rings.chem
@@ -0,0 +1,43 @@
+chBc_rings.chem:
+.br
+.cstart
+
+# Example file for 'chem':
+
+# This originates from Computing Science Technical Report No. 122
+# CHEM - A Program for Typesetting Chemical Diagrams: User Manual
+# by Jon L. Bentley, Lynn W. Jelinski, Brian W. Kernighan
+# <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+########################################################################
+
+R1: benzene
+ bond -120 from R1.V5 ; CH3O
+R2: ring4 pointing 45 with .V4 at R1.V2
+R3: aromatic ring6 put N at 4 put S at 2 at R2 + (.75,0)
+R4: ring5 pointing left at R3 + (.75,0)
+ label R4
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/README.txt b/contrib/chem/examples/README.txt
new file mode 100644
index 0000000..6786705
--- /dev/null
+++ b/contrib/chem/examples/README.txt
@@ -0,0 +1,47 @@
+This directory contains examples for the 'chem' language.
+
+You can view the graphical display of the examples by calling
+
+ @g@chem <file> | groff -p ...
+
+On the displays, you can see rings consisting of several lines and
+bonds (lines). All points on rings and bonds that do not have a
+notation mean a C atom (carbon) filled with H atoms (hydrogen) such
+that the valence of 4 is satisfied.
+
+For example, suppose you have just a single line without any
+characters. That means a bond. It has two points, one at each end of
+the line. So each of these points stands for a C atom, the bond
+itself connects these 2 C atoms. To fulfill the valence of 4, each
+points has to carry additionally 3 H atoms. So the single empty bond
+stands for CH3-CH3, though this combination doesn't make much sense
+chemically.
+
+
+####### License
+
+Copyright (C) 2006-2020 Free Software Foundation, Inc.
+Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+This file is part of 'chem', which is part of 'groff'.
+
+'groff' is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+'groff' is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+The GPL2 license text is available in the internet at
+<http://www.gnu.org/licenses/gpl-2.0.html>.
+
+
+##### Editor settings
+Local Variables:
+fill-column: 72
+mode: text
+End:
+vim: set textwidth=72:
diff --git a/contrib/chem/examples/atp.chem b/contrib/chem/examples/atp.chem
new file mode 100644
index 0000000..738c4da
--- /dev/null
+++ b/contrib/chem/examples/atp.chem
@@ -0,0 +1,58 @@
+atp.chem:
+.cstart
+
+# Example file for 'chem':
+# ATP or C10_H16_N5_O13_P3 or
+# [[[5-(6-aminopurin-9-yl)-3,4-dihydroxy-oxolan-2-yl]methoxy-hydroxy-
+# phosphoryl]oxy-hydroxy-phosphoryl]oxyphosphonic acid
+
+# Found at http://www.chemindustry.com/apps/chemicals.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+# Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+R1: ring5 pointing left double 1,2 3,4 put N at 2 put N at 5
+B: benzene put N at 2 with .V6 at R1.V3 with .V5 at R1.V4
+ bond up ; NH2
+ backbond 170 length .7 from R1.V5
+R2: ring5 pointing down with .V2 put O at 1
+ bond down at R2.V2 ; H
+ bond down length .1 at R2.V3 ; H
+ bond up length .1 at R2.V3 ; OH
+ bond down length .1 at R2.V4 ; H
+ bond up length .1 at R2.V4 ; OH
+ frontbond 70 at R2.V5
+ bond 110 ; O
+ bond right ; P
+ doublebond up ; O
+ bond down from P ; OH
+ bond right from P ; O
+ bond right ; P
+ doublebond up ; O
+ bond down from P ; OH
+ bond right from P ; O
+ bond right ; P
+ doublebond up ; O
+ bond down from P ; OH
+ bond right from P ; OH
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+.cend
diff --git a/contrib/chem/examples/cholesterin.chem b/contrib/chem/examples/cholesterin.chem
new file mode 100644
index 0000000..12ac076
--- /dev/null
+++ b/contrib/chem/examples/cholesterin.chem
@@ -0,0 +1,47 @@
+cholesterin.chem:
+.cstart
+
+# Example file for 'chem':
+# Cholesterin or C27_H46O or
+# 10,13-dimethyl-17-(6-methylheptan-2-yl)-2,3,4,5,6,9,11,12,14,15,16,17-
+# dodecahydro-1H-cyclopenta[a]phenanthren-3-ol
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+# Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+R1: ring6
+ bond -120 ; HO
+R2: ring6 with .V5 at R1.V3 with .V6 at R1.V2 double 4,5
+ bond up at R2.V6
+R3: ring6 with .V5 at R2.V1 with .V4 at R2.V2
+R4: flatring5 pointing up with .V4 at R3.V3 with .V5 at R3.V2
+ bond up at R4.V5
+ bond up at R4.V1
+B1: bond -60
+ bond 60 at B1.start
+ bond 120
+ bond 60
+ bond 120
+B2: bond 60
+ bond down at B2.start
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+.cend
diff --git a/contrib/chem/examples/ethamivan.chem b/contrib/chem/examples/ethamivan.chem
new file mode 100644
index 0000000..a0a8aa2
--- /dev/null
+++ b/contrib/chem/examples/ethamivan.chem
@@ -0,0 +1,43 @@
+ethamivan.chem:
+.cstart
+
+# Example file for 'chem':
+# Ethamivan or Analepticon or C12_H17_N_O3 or
+# N,N-diethyl-4-hydroxy-3-methoxy-benzamide
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+# Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+R: ring pointing left double 2,3 4,5 6,1
+ bond left from R.V1 ; O
+ bond left ; H
+ bond -150 from R.V6 ; O
+ bond left
+ bond 60 from R.V4
+B1: double bond up ; O
+ bond 120 from B1.start ; N
+ bond 45
+ bond right
+ bond 135 from N
+ bond right
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+.cend
diff --git a/contrib/chem/examples/lsd.chem b/contrib/chem/examples/lsd.chem
new file mode 100644
index 0000000..4879ea8
--- /dev/null
+++ b/contrib/chem/examples/lsd.chem
@@ -0,0 +1,46 @@
+lsd.chem:
+.cstart
+
+# Example file for 'chem':
+# LSD or Lysergic acid dethylamide or C20_H25_N3O or
+# 9,10-Didehydro-N,N-diethyl-6-methyl-ergoline-8-beta-carboxamide
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+# Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+F: flatring5 pointing left put N at 5 double 3,4
+ H below F.N
+B: benzene pointing right with .V1 at F.V2
+R1: ring pointing right with .V4 at B.V6
+ front bond right from R1.V6 ; H
+R2: ring pointing right with .V2 at R1.V6 put N at 1 double 3,4
+ bond right from R2.N
+ back bond -60 from R2.V5 ; H
+ bond up from R2.V5
+B1: double bond up ; O
+ bond right from B1.start ; N
+ bond 45
+ bond right
+ bond 135 from N
+ bond right
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+.cend
diff --git a/contrib/chem/examples/morphine.chem b/contrib/chem/examples/morphine.chem
new file mode 100644
index 0000000..5c236ca
--- /dev/null
+++ b/contrib/chem/examples/morphine.chem
@@ -0,0 +1,51 @@
+morphine.chem:
+.cstart
+
+# Example file for 'chem':
+# Morphine or C23_H31_N3O or
+# N,N-diethyl-N'-(2-methoxyacridin-9-yl)-pentane-1,4-diamine
+
+# Found at http://www.chemindustry.com/apps/chemicals.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+# Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+R1: benzene
+R2: benzene with .V6 at R1.V2 with .V5 at R1.V3 put N at 4
+R3: benzene with .V6 at R2.V2 with .V5 at R2.V3
+ bond 60 at R3.V2 ; O
+ bond 120
+ bond up at R2.V1 ; N
+ bond 60 ; H
+ bond -60 at N
+B1: backbond -120
+ bond up at B1.start
+ bond -60
+ bond up
+ bond -60 ; N
+ bond up
+ bond -60
+ bond -120 at N
+ bond -60
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/penicillin.chem b/contrib/chem/examples/penicillin.chem
new file mode 100644
index 0000000..ef522bc
--- /dev/null
+++ b/contrib/chem/examples/penicillin.chem
@@ -0,0 +1,52 @@
+penicillin.chem:
+.cstart
+
+# Example file for 'chem':
+# Penicillin or C16_H18_N2_O4_S or
+# 3,3-dimethyl-6-oxo-7-(2-phenylacetyl)amino-2-thia-5-
+# azabicyclo[3.2.0]heptane-4-carboxylic acid
+
+# Found at http://www.chemindustry.com/apps/chemicals.
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+# Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+R1: flatring5 pointing up put S at 1 put N at 4
+ bond 45 at R1.V2
+ bond 135 at R1.V2
+ bond 120 at R1.V3
+D1: doublebond 45 ; O
+ bond 135 at D1.start ; OH
+ bond left at R1.N
+ doublebond -135 ; O
+ bond left at R1.V5
+B1: bond down length .3
+ bond -60 at B1.start ; N
+ bond up ; H
+ bond -120 at N
+D2: doublebond down ; O
+ bond -60 at D2.start
+ bond -120
+ benzene
+
+# Local Variables:
+# mode: Nroff
+# End:
+.cend
diff --git a/contrib/chem/examples/reserpine.chem b/contrib/chem/examples/reserpine.chem
new file mode 100644
index 0000000..d1b4046
--- /dev/null
+++ b/contrib/chem/examples/reserpine.chem
@@ -0,0 +1,63 @@
+reserpine.chem:
+.PS
+begin chem
+
+# Example file for 'chem':
+# Reserpine or C33H40N2O9
+
+# Copyright (C) 2006-2020 Free Software Foundation, Inc.
+# Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+# This file is part of 'chem', which is part of 'groff'.
+
+# 'groff' is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License (GPL) version 2 as
+# published by the Free Software Foundation.
+
+# 'groff' is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# The GPL2 license text is available in the internet at
+# <http://www.gnu.org/licenses/gpl-2.0.html>.
+
+R1: benzene pointing up
+ bond -120 from R1.V5 ; O
+ bond left
+R2: flatring5 pointing down double 4,5 with .V2 at R1.V3 with .V3 at R1.V2 put N at 1
+ H below R2.V1
+R3: ring put N at 3 with .V5 at R2.V5
+R4: ring put N at 1 with .V1 at R3.V3
+ back bond -120 from R4.V4 ; H
+ back bond 60 from R4.V3 ; H
+R5: ring with .V1 at R4.V3
+ bond -120
+D1: double bond down ; O
+ bond left from D1.start ; O
+ bond left
+ back bond 60 from R5.V3 ; H
+ back bond down from R5.V4 ; O
+ bond down from O
+ bond 120 from R5.V3 ; O
+ bond 50 from O
+D2: double bond up ; O
+ bond right length .1 from D2.start
+B: benzene pointing right
+ bond 45 from B.V6 ; O
+ bond right
+ bond right from B.V1 ; O
+ bond right
+ bond 135 from B.V2 ; O
+ bond right
+
+# Local Variables:
+# fill-column: 72
+# mode: Nroff
+# End:
+# vim: set textwidth=72:
+end
+.PE