From e1270f81bdc81f5a575b34c2d2c294bdde3e6f4f Mon Sep 17 00:00:00 2001
From: Nathan Binkert <nate@binkert.org>
Date: Sun, 16 Aug 2009 13:39:58 -0700
Subject: ply: update PLY to version 3.2
---
ext/ply/example/closurecalc/calc.py | 130 ++++++++++++++++++++++++++++++++++++
1 file changed, 130 insertions(+)
create mode 100644 ext/ply/example/closurecalc/calc.py
(limited to 'ext/ply/example/closurecalc/calc.py')
diff --git a/ext/ply/example/closurecalc/calc.py b/ext/ply/example/closurecalc/calc.py
new file mode 100644
index 000000000..6598f5844
--- /dev/null
+++ b/ext/ply/example/closurecalc/calc.py
@@ -0,0 +1,130 @@
+# -----------------------------------------------------------------------------
+# calc.py
+#
+# A calculator parser that makes use of closures. The function make_calculator()
+# returns a function that accepts an input string and returns a result. All
+# lexing rules, parsing rules, and internal state are held inside the function.
+# -----------------------------------------------------------------------------
+
+import sys
+sys.path.insert(0,"../..")
+
+if sys.version_info[0] >= 3:
+ raw_input = input
+
+# Make a calculator function
+
+def make_calculator():
+ import ply.lex as lex
+ import ply.yacc as yacc
+
+ # ------- Internal calculator state
+
+ variables = { } # Dictionary of stored variables
+
+ # ------- Calculator tokenizing rules
+
+ tokens = (
+ 'NAME','NUMBER',
+ )
+
+ literals = ['=','+','-','*','/', '(',')']
+
+ t_ignore = " \t"
+
+ t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
+
+ def t_NUMBER(t):
+ r'\d+'
+ t.value = int(t.value)
+ return 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
+ lexer = lex.lex()
+
+ # ------- Calculator parsing rules
+
+ precedence = (
+ ('left','+','-'),
+ ('left','*','/'),
+ ('right','UMINUS'),
+ )
+
+ def p_statement_assign(p):
+ 'statement : NAME "=" expression'
+ variables[p[1]] = p[3]
+ p[0] = None
+
+ def p_statement_expr(p):
+ 'statement : expression'
+ p[0] = p[1]
+
+ def p_expression_binop(p):
+ '''expression : expression '+' expression
+ | expression '-' expression
+ | expression '*' expression
+ | expression '/' expression'''
+ if p[2] == '+' : p[0] = p[1] + p[3]
+ elif p[2] == '-': p[0] = p[1] - p[3]
+ elif p[2] == '*': p[0] = p[1] * p[3]
+ elif p[2] == '/': p[0] = p[1] / p[3]
+
+ def p_expression_uminus(p):
+ "expression : '-' expression %prec UMINUS"
+ p[0] = -p[2]
+
+ def p_expression_group(p):
+ "expression : '(' expression ')'"
+ p[0] = p[2]
+
+ def p_expression_number(p):
+ "expression : NUMBER"
+ p[0] = p[1]
+
+ def p_expression_name(p):
+ "expression : NAME"
+ try:
+ p[0] = variables[p[1]]
+ except LookupError:
+ print("Undefined name '%s'" % p[1])
+ p[0] = 0
+
+ def p_error(p):
+ if p:
+ print("Syntax error at '%s'" % p.value)
+ else:
+ print("Syntax error at EOF")
+
+
+ # Build the parser
+ parser = yacc.yacc()
+
+ # ------- Input function
+
+ def input(text):
+ result = parser.parse(text,lexer=lexer)
+ return result
+
+ return input
+
+# Make a calculator object and use it
+calc = make_calculator()
+
+while True:
+ try:
+ s = raw_input("calc > ")
+ except EOFError:
+ break
+ r = calc(s)
+ if r:
+ print(r)
+
+
--
cgit v1.2.3