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+# arrayops.bash --- hide some of the nasty syntax for manipulating bash arrays
+# Author: Noah Friedman <friedman@splode.com>
+# Created: 2016-07-08
+# Public domain
+
+# $Id: arrayops.bash,v 1.3 2016/07/28 15:38:55 friedman Exp $
+
+# Commentary:
+
+# These functions try to tame the syntactic nightmare that is bash array
+# syntax, which makes perl's almost look reasonable.
+#
+# For example the apush function below lets you write:
+#
+#	apush arrayvar newval
+#
+# instead of
+#
+#	${arrayvar[${#arrayvar[@]}]}=newval
+#
+# Because seriously, you've got to be kidding me.
+
+# These functions avoid the use of local variables as much as possible
+# (especially wherever modification occurs) because those variable names
+# might shadow the array name passed in.  Dynamic scope!
+
+# Code:
+
+#:docstring apush:
+# Usage: apush arrayname val1 {val2 {...}}
+#
+# Appends VAL1 and any remaining arguments to the end of the array
+# ARRAYNAME as new elements.
+#:end docstring:
+apush()
+{
+    eval "$1=(\"\${$1[@]}\" \"\${@:2}\")"
+}
+
+#:docstring apop:
+# Usage: apop arrayname {n}
+#
+# Removes the last element from ARRAYNAME.
+# Optional argument N means remove the last N elements.
+#:end docstring:
+apop()
+{
+    eval "$1=(\"\${$1[@]:0:\${#$1[@]}-${2-1}}\")"
+}
+
+#:docstring aunshift:
+# Usage: aunshift arrayname val1 {val2 {...}}
+#
+# Prepends VAL1 and any remaining arguments to the beginning of the array
+# ARRAYNAME as new elements.  The new elements will appear in the same order
+# as given to this function, rather than inserting them one at a time.
+#
+# For example:
+#
+#	foo=(a b c)
+#	aunshift foo 1 2 3
+#       => foo is now (1 2 3 a b c)
+# but
+#
+#	foo=(a b c)
+#	aunshift foo 1
+#       aunshift foo 2
+#       aunshift foo 3
+#       => foo is now (3 2 1 a b c)
+#
+#:end docstring:
+aunshift()
+{
+    eval "$1=(\"\${@:2}\" \"\${$1[@]}\")"
+}
+
+#:docstring ashift:
+# Usage: ashift arrayname {n}
+#
+# Removes the first element from ARRAYNAME.
+# Optional argument N means remove the first N elements.
+#:end docstring:
+ashift()
+{
+    eval "$1=(\"\${$1[@]: -\${#$1[@]}+${2-1}}\")"
+}
+
+#:docstring aset:
+# Usage: aset arrayname idx newval
+#
+# Assigns ARRAYNAME[IDX]=NEWVAL
+#:end docstring:
+aset()
+{
+    eval "$1[\$2]=${@:3}"
+}
+
+#:docstring aref:
+# Usage: aref arrayname idx {idx2 {...}}
+#
+# Echoes the value of ARRAYNAME at index IDX to stdout.
+# If more than one IDX is specified, each one is echoed.
+#
+# Unfortunately bash functions cannot return arbitrary values in the usual way.
+#:end docstring:
+aref()
+{
+    eval local "v=(\"\${$1[@]}\")"
+    local x
+    for x in ${@:2} ; do echo "${v[$x]}"; done
+}
+
+#:docstring aref:
+# Usage: alen arrayname
+#
+# Echoes the length of the number of elements in ARRAYNAME.
+#
+# It also returns number as a numeric value, but return values are limited
+# by a maximum of 255 so don't rely on this unless you know your arrays are
+# relatively small.
+#:end docstring:
+alen()
+{
+    eval echo   "\${#$1[@]}"
+    eval return "\${#$1[@]}"
+}
+
+#:docstring anreverse:
+# Usage: anreverse arrayname
+#
+# Reverse the order of the elements in ARRAYNAME.
+# The array variable is altered by this operation.
+#:end docstring:
+anreverse()
+{
+    eval set $1 "\"\${$1[@]}\""
+    eval unset $1
+    while [ $# -gt 1 ]; do
+        eval "$1=(\"$2\" \"\${$1[@]}\")"
+        set $1 "${@:3}"
+    done
+}
+
+#provide arrayops
+
+# arrayops.bash ends here