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Solver.py
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Solver.py
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# MATH FORMULAS SOLVER FOR FALLUTO2.1
# Uses externals pyPEG and re
# Raul Monti
# 29/03/2014 01:05:05
# Falluto2.1
from pyPEG import parseLine, Symbol
import re
from Utils import ast2str
# Parsing rules ================================================================
__rc = re.compile
def SUM(): return PROD, -1, (__rc(r'[\+\-]'), PROD)
def PROD(): return VAL, -1, (__rc(r'[\*\/\%]'), VAL)
def VAL(): return 0, __rc(r'\-'), [ __rc(r'\d+')
, (__rc(r'\('), SUM, __rc('\)'))
, NAME
]
def NAME(): return __rc(r"[a-zA-Z_]+\w*")
# Exceptions ===================================================================
class NotMath(Exception):
def __init__(self, error):
Exception.__init__(self)
self.err = str(error) + " is not a math formula."
def __str__(self):
return self.err
class NoName(Exception):
def __init__(self, error):
Exception.__init__(self)
self.err = "<" + str(error) + "> doesn't name a constant"\
+ " value in the model."
def __str__(self):
return self.err
# The Solver Class =============================================================
class Solver():
mainSolver = None # The main solver object.
def __init__(self):
self.defTable = {} # Name -- Definition.
Solver.mainSolver = self # The main solver object corresponds to the
# last solver instantiated.
def populateDefsTable(self, defs):
""" @ warning: defs should be a list of pairs (name, definition)
"""
for k,v in defs:
# WARNING, it runs over old values if two keys are the same as it's
# a dictionary.
self.defTable[k] = v
def solveMath(self, formula):
assert isinstance(formula, str)
_result = 0
p, rest = parseLine(formula, SUM, resultSoFar=[])
if rest:
raise NotMath(formula)
try:
_result = self.solveSum(p[0])
except NoName as e:
raise Exception("Can't solve " + formula + " because: " + str(e))
return _result
def solveSum(self, ast):
assert isinstance(ast, Symbol)
assert ast.__name__ == 'SUM'
_result = 0
_vs = ast.what[::2] # values
_os = [o for o in ast.what[1::2]] # operators
_vss = [self.solveProd(v) for v in _vs]
_result = _vss[0]
assert len(_os) == len(_vss[1:])
for o,v in zip(_os,_vss[1:]):
if o == '+':
_result += v
elif o == '-':
_result -= v
else:
assert False
return _result
def solveProd(self, ast):
assert isinstance(ast, Symbol)
assert ast.__name__ == 'PROD'
_result = 0
_vs = ast.what[::2] # values
_os = [ast2str(o) for o in ast.what[1::2]] # operators
_vss = [self.solveVal(v) for v in _vs]
_result = _vss[0]
assert len(_os) == len(_vss[1:])
for o,v in zip(_os,_vss[1:]):
if o == '*':
_result *= v
elif o == '/':
_result /= v
elif o == '%':
_result %= v
else:
assert False
return _result
def solveVal(self, ast):
assert isinstance(ast, Symbol)
assert ast.__name__ == 'VAL'
_result = 0
_sign = 1
_aw = ast.what
if _aw[0] == u'-':
# it's a negative value
_sign = -1
_aw = _aw[1:]
if _aw[0] == '(':
# it's a SUM formula inside brackets
_result = self.solveSum(_aw[1])
elif isinstance(_aw[0], unicode) or isinstance(_aw[0], str):
# it's a number as its not '('
_result = int(_aw[0])
elif isinstance(_aw[0], Symbol):
#it's a NAME
_def = ""
try:
_def = self.defTable[str(ast2str(_aw[0]))]
except:
raise NoName(ast2str(_aw[0]))
_result = self.solveMath(str(ast2str(_def)))
else:
raise TypeError(_aw[0])
return _sign*_result
# MAIN =========================================================================
if __name__ == '__main__':
svr = Solver()
svr.defTable['A'] = '1'
svr.defTable['B'] = '2'
svr.defTable['C'] = '3'
print ">>", svr.solveMath('(A+(B*C)--1)/4')
print ">>", svr.solveMath('A+(B*C)')
print ">>", svr.solveMath('(A+B)*C')
print ">>", svr.solveMath('1')
print ">>", svr.solveMath('(A+(D*C)--1)/4')