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#! /usr/bin/env python
# Copyright (c) 2007-2008 PediaPress GmbH
# See README.txt for additional licensing information.
# based on pyparsing example code (SimpleCalc.py)
"""Implementation of mediawiki's #expr template.
http://meta.wikimedia.org/wiki/ParserFunctions#.23expr:
"""
from __future__ import division
import re
import inspect
import math
class ExprError(Exception):
pass
def _myround(a,b):
r=round(a, int(b))
if int(r)==r:
return int(r)
return r
pattern = """
(?:\s+)
|((?:(?:\d+)(?:\.\d+)?
|(?:\.\d+)) (?:e(?:\+|-)?\d+)?)
|(\+|-|\*|/|>=|<=|<>|!=|[a-zA-Z]+|.)
"""
rxpattern = re.compile(pattern, re.VERBOSE | re.DOTALL | re.IGNORECASE)
def tokenize(s):
res = []
for (v1,v2) in rxpattern.findall(s):
if not (v1 or v2):
continue
v2=v2.lower()
if v2 in Expr.constants:
res.append((v2,""))
else:
res.append((v1,v2))
return res
return [(v1,v2.lower()) for (v1,v2) in rxpattern.findall(s) if v1 or v2]
class uminus: pass
class uplus: pass
precedence = {"(":-1, ")":-1}
functions = {}
def addop(op, prec, fun, numargs=None):
precedence[op] = prec
if numargs is None:
numargs = len(inspect.getargspec(fun)[0])
def wrap(stack):
assert len(stack)>=numargs
args = tuple(stack[-numargs:])
del stack[-numargs:]
stack.append(fun(*args))
functions[op] = wrap
a=addop
a(uminus, 10, lambda x: -x)
a(uplus, 10, lambda x: x)
a("^", 10, math.pow, 2)
a("not", 9, lambda x:int(not(bool(x))))
a("abs", 9, abs, 1)
a("sin", 9, math.sin, 1)
a("cos", 9, math.cos, 1)
a("asin", 9, math.asin, 1)
a("acos", 9, math.acos, 1)
a("tan", 9, math.tan, 1)
a("atan", 9, math.atan, 1)
a("exp", 9, math.exp, 1)
a("ln", 9, math.log, 1)
a("ceil", 9, lambda x: int(math.ceil(x)))
a("floor", 9, lambda x: int(math.floor(x)))
a("trunc", 9, long, 1)
a("*", 8, lambda x,y: x*y)
a("/", 8, lambda x,y: x/y)
a("div", 8, lambda x,y: x/y)
a("mod", 8, lambda x,y: int(x)%int(y))
a("+", 6, lambda x,y: x+y)
a("-", 6, lambda x,y: x-y)
a("round", 5, _myround)
a("<", 4, lambda x,y: int(x<y))
a(">", 4, lambda x,y: int(x>y))
a("<=", 4, lambda x,y: int(x<=y))
a(">=", 4, lambda x,y: int(x>=y))
a("!=", 4, lambda x,y: int(x!=y))
a("<>", 4, lambda x,y: int(x!=y))
a("=", 4, lambda x,y: int(x==y))
a("and", 3, lambda x,y: int(bool(x) and bool(y)))
a("or", 2, lambda x,y: int(bool(x) or bool(y)))
del a
class Expr(object):
constants = dict(
e=math.e,
pi=math.pi)
def as_float_or_int(self, s):
try:
return self.constants[s]
except KeyError:
pass
if "." in s or "e" in s.lower():
return float(s)
return long(s)
def output_operator(self, op):
return functions[op](self.operand_stack)
def output_operand(self, operand):
self.operand_stack.append(operand)
def parse_expr(self, s):
tokens = tokenize(s)
if not tokens:
return ""
self.operand_stack = []
operator_stack = []
seen_operand=False
last_operand, last_operator = False, True
for operand, operator in tokens:
if operand:
if last_operand:
raise ExprError("expected operator")
self.output_operand(self.as_float_or_int(operand))
elif operator=="(":
operator_stack.append("(")
elif operator==")":
while 1:
if not operator_stack:
raise ExprError("unbalanced parenthesis")
t = operator_stack.pop()
if t=="(":
break
self.output_operator(t)
elif operator in precedence:
if last_operator and last_operator!=")":
if operator=='-':
operator = uminus
elif operator=='+':
operator = uplus
is_unary = operator in (uplus, uminus)
prec = precedence[operator]
while not is_unary and operator_stack and prec<=precedence[operator_stack[-1]]:
p = operator_stack.pop()
self.output_operator(p)
operator_stack.append(operator)
else:
raise ExprError("unknown operator: %r" % (operator,))
last_operand, last_operator = operand, operator
while operator_stack:
p=operator_stack.pop()
if p=="(":
raise ExprError("unbalanced parenthesis")
self.output_operator(p)
if len(self.operand_stack)!=1:
raise ExprError("bad stack: %s" % (self.operand_stack,))
return self.operand_stack[-1]
def expr(s):
return Expr().parse_expr(s)
def main():
ParseException = ExprError
import time
try:
import readline # do not remove. makes raw_input use readline
readline
except ImportError:
pass
ep = expr
while 1:
input_string = raw_input("> ")
if not input_string:
continue
stime = time.time()
try:
res=expr(input_string)
except Exception, err:
print "ERROR:", err
import traceback
traceback.print_exc()
continue
print res
print time.time()-stime, "s"
if __name__=='__main__':
main()
|
