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-rw-r--r--third_party/python/ply/example/optcalc/README9
-rw-r--r--third_party/python/ply/example/optcalc/calc.py134
2 files changed, 143 insertions, 0 deletions
diff --git a/third_party/python/ply/example/optcalc/README b/third_party/python/ply/example/optcalc/README
new file mode 100644
index 0000000000..53dd5fcd55
--- /dev/null
+++ b/third_party/python/ply/example/optcalc/README
@@ -0,0 +1,9 @@
+An example showing how to use Python optimized mode.
+To run:
+
+ - First run 'python calc.py'
+
+ - Then run 'python -OO calc.py'
+
+If working correctly, the second version should run the
+same way.
diff --git a/third_party/python/ply/example/optcalc/calc.py b/third_party/python/ply/example/optcalc/calc.py
new file mode 100644
index 0000000000..0c223e5994
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+++ b/third_party/python/ply/example/optcalc/calc.py
@@ -0,0 +1,134 @@
+# -----------------------------------------------------------------------------
+# calc.py
+#
+# A simple calculator with variables. This is from O'Reilly's
+# "Lex and Yacc", p. 63.
+# -----------------------------------------------------------------------------
+
+import sys
+sys.path.insert(0, "../..")
+
+if sys.version_info[0] >= 3:
+ raw_input = input
+
+tokens = (
+ 'NAME', 'NUMBER',
+ 'PLUS', 'MINUS', 'TIMES', 'DIVIDE', 'EQUALS',
+ 'LPAREN', 'RPAREN',
+)
+
+# Tokens
+
+t_PLUS = r'\+'
+t_MINUS = r'-'
+t_TIMES = r'\*'
+t_DIVIDE = r'/'
+t_EQUALS = r'='
+t_LPAREN = r'\('
+t_RPAREN = r'\)'
+t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
+
+
+def t_NUMBER(t):
+ r'\d+'
+ try:
+ t.value = int(t.value)
+ except ValueError:
+ print("Integer value too large %s" % t.value)
+ t.value = 0
+ return t
+
+t_ignore = " \t"
+
+
+def t_newline(t):
+ r'\n+'
+ t.lexer.lineno += t.value.count("\n")
+
+
+def t_error(t):
+ print("Illegal character '%s'" % t.value[0])
+ t.lexer.skip(1)
+
+# Build the lexer
+import ply.lex as lex
+lex.lex(optimize=1)
+
+# Parsing rules
+
+precedence = (
+ ('left', 'PLUS', 'MINUS'),
+ ('left', 'TIMES', 'DIVIDE'),
+ ('right', 'UMINUS'),
+)
+
+# dictionary of names
+names = {}
+
+
+def p_statement_assign(t):
+ 'statement : NAME EQUALS expression'
+ names[t[1]] = t[3]
+
+
+def p_statement_expr(t):
+ 'statement : expression'
+ print(t[1])
+
+
+def p_expression_binop(t):
+ '''expression : expression PLUS expression
+ | expression MINUS expression
+ | expression TIMES expression
+ | expression DIVIDE expression'''
+ if t[2] == '+':
+ t[0] = t[1] + t[3]
+ elif t[2] == '-':
+ t[0] = t[1] - t[3]
+ elif t[2] == '*':
+ t[0] = t[1] * t[3]
+ elif t[2] == '/':
+ t[0] = t[1] / t[3]
+ elif t[2] == '<':
+ t[0] = t[1] < t[3]
+
+
+def p_expression_uminus(t):
+ 'expression : MINUS expression %prec UMINUS'
+ t[0] = -t[2]
+
+
+def p_expression_group(t):
+ 'expression : LPAREN expression RPAREN'
+ t[0] = t[2]
+
+
+def p_expression_number(t):
+ 'expression : NUMBER'
+ t[0] = t[1]
+
+
+def p_expression_name(t):
+ 'expression : NAME'
+ try:
+ t[0] = names[t[1]]
+ except LookupError:
+ print("Undefined name '%s'" % t[1])
+ t[0] = 0
+
+
+def p_error(t):
+ if t:
+ print("Syntax error at '%s'" % t.value)
+ else:
+ print("Syntax error at EOF")
+
+import ply.yacc as yacc
+yacc.yacc(optimize=1)
+
+while 1:
+ try:
+ s = raw_input('calc > ')
+ except EOFError:
+ break
+ yacc.parse(s)