coding utf-8 from pyparsing import Literal CaselessLiteral Word Combin

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# -*- coding: utf-8 -*-
from pyparsing import Literal,CaselessLiteral,Word,Combine,Group,Optional,\
ZeroOrMore,Forward,nums,alphas
import math
import operator
exprStack = []
def pushFirst( strg, loc, toks ):
exprStack.append( toks[0] )
def pushUMinus( strg, loc, toks ):
if toks and toks[0]=='-':
exprStack.append( 'unary -' )
#~ exprStack.append( '-1' )
#~ exprStack.append( '*' )
def logical_not(a):
"""Logical not"""
if a is "F":
return "T"
if a is "T":
return "F"
raise Exception('MyExeption', 'MyExeption')
def lgc_nequal(a,b):
"""Logical !="""
try:
x = float(a)
y = float(b)
except ValueError:
if a!=b:
return "T"
if a==b:
return "F"
raise Exception('MyExeption', 'MyExeption')
if x!=y:
return "T"
if x==y:
return "F"
raise Exception('MyExeption', 'MyExeption')
def lgc_nmore(a,b):
"""Logical <="""
if type(a) is float and type(b) is float:
if a<=b:
return "T"
else:
return "F"
raise Exception('MyExeption', 'MyExeption')
def lgc_nless(a,b):
"""Logical >="""
if type(a) is float and type(b) is float:
if a>=b:
return "T"
else:
return "F"
raise Exception('MyExeption', 'MyExeption')
bnf = None
def BNF():
"""
expop :: '^'
multop :: '*' | '/'
addop :: '+' | '-'
integer :: ['+' | '-'] '0'..'9'+
atom :: PI | E | real | fn '(' expr ')' | '(' expr ')'
factor :: atom [ expop factor ]*
term :: factor [ multop factor ]*
expr :: term [ addop term ]*
lgc :: expr [ logicalop expr]*
"""
global bnf
if not bnf:
point = Literal( "." )
e = CaselessLiteral( "E" )
fnumber = Combine( Word( "+-"+nums, nums ) +
Optional( point + Optional( Word( nums ) ) ) +
Optional( e + Word( "+-"+nums, nums ) ) )
T = CaselessLiteral("T")
F = CaselessLiteral("F")
ident = Word(alphas, alphas+nums+"_$")
plus = Literal( "+" )
minus = Literal( "-" )
mult = Literal( "*" )
div = Literal( "/" )
lpar = Literal( "(" ).suppress()
rpar = Literal( ")" ).suppress()
pmod = CaselessLiteral( "mod" )
pdiv = CaselessLiteral( "div" )
nbiger = Literal( "<=" )
nless = Literal( ">=" )
nequal = Literal( "<>" )
addop = plus | minus
multop = mult | div | pmod | pdiv
logicalop = nbiger | nless | nequal
expop = Literal( "^" )
pi = CaselessLiteral( "PI" )
expr = Forward()
lgc = Forward()
atom = (Optional("-") + ( pi | e | fnumber | T | F | ident + lpar + expr + rpar ).setParseAction( pushFirst ) | ( lpar + expr.suppress() + rpar )).setParseAction(pushUMinus)
# by defining exponentiation as "atom [ ^ factor ]..." instead of "atom [ ^ atom ]...", we get right-to-left exponents, instead of left-to-righ
# that is, 2^3^2 = 2^(3^2), not (2^3)^2.
factor = Forward()
factor << atom + ZeroOrMore( ( expop + factor ).setParseAction( pushFirst ) )
term = factor + ZeroOrMore( ( multop + factor ).setParseAction( pushFirst ) )
expr << term + ZeroOrMore( ( addop + term ).setParseAction( pushFirst ) )
lgc = expr + ZeroOrMore( ( logicalop + expr ).setParseAction(pushFirst) )
bnf = lgc
return bnf
# map operator symbols to corresponding arithmetic operations
epsilon = 1e-12
opn = { "+" : operator.add,
"-" : operator.sub,
"*" : operator.mul,
"/" : operator.truediv,
"^" : operator.pow,
"div": operator.floordiv,
"mod": operator.mod,
"<=" : lgc_nmore,
">=" : lgc_nless,
"<>" : lgc_nequal }
fn = { "not" : logical_not,
"sin" : math.sin,
"cos" : math.cos,
"tan" : math.tan,
"abs" : abs,
"trunc" : lambda a: int(a),
"round" : round,
"sgn" : lambda a: abs(a)>epsilon and cmp(a,0) or 0}
def evaluateStack( s ):
op = s.pop()
if op == 'unary -':
return -evaluateStack( s )
if op in opn.keys(): #"+-*/^" or op is "mod" or op is "div":
op2 = evaluateStack( s )
op1 = evaluateStack( s )
return opn[op]( op1, op2 )
elif op == "PI":
return math.pi # 3.1415926535
elif op == "E":
return math.e # 2.718281828
elif op in fn:
return fn[op]( evaluateStack( s ) )
elif op is "T" or op is "F":
return op
elif op[0].isalpha():
return 0
else:
try:
return float( op )
except ValueError:
raise Exception('MyExeption', 'MyExeption')
if __name__ == "__main__":
def test( s, expVal ):
global exprStack
exprStack = []
results = BNF().parseString( s )
val = evaluateStack( exprStack[:] )
print '"'+s+'"'+' ==',val,' => ', results, ' => ', exprStack
#if val == expVal:
#print s, "=", val, results, "=>", exprStack
#else:
# print s+"!!!", val, "!=", expVal, results, "=>", exprStack
test("T<>(7<>8)<>T", 0) #T<>(7<>8)<>T