132 lines
5.0 KiB
Python
132 lines
5.0 KiB
Python
import math
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import operator
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from pyparsing import Word, alphas, nums, oneOf, Literal
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from pyparsing import ZeroOrMore, OneOrMore, StringStart
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from pyparsing import StringEnd, Optional, Forward
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from pyparsing import CaselessLiteral, Group, StringEnd
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from pyparsing import NoMatch, stringEnd
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def evaluator(variables, functions, string):
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''' Evaluate an expression. Variables are passed as a dictionary
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from string to value. Unary functions are passed as a dictionary
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from string to function '''
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if string.strip() == "":
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return float('nan')
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ops = { "^" : operator.pow,
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"*" : operator.mul,
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"/" : operator.truediv,
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"+" : operator.add,
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"-" : operator.sub,
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}
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# We eliminated extreme ones, since they're rarely used, and potentially
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# confusing. They may also conflict with variables if we ever allow e.g.
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# 5R instead of 5*R
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suffixes={'%':0.01,'k':1e3,'M':1e6,'G':1e9,
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'T':1e12,#'P':1e15,'E':1e18,'Z':1e21,'Y':1e24,
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'c':1e-2,'m':1e-3,'u':1e-6,
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'n':1e-9,'p':1e-12}#,'f':1e-15,'a':1e-18,'z':1e-21,'y':1e-24}
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def super_float(text):
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''' Like float, but with si extensions. 1k goes to 1000'''
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if text[-1] in suffixes:
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return float(text[:-1])*suffixes[text[-1]]
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else:
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return float(text)
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def number_parse_action(x): # [ '7' ] -> [ 7 ]
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return [super_float("".join(x))]
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def exp_parse_action(x): # [ 2 ^ 3 ^ 2 ] -> 512
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x = [e for e in x if type(e) == float] # Ignore ^
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x.reverse()
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x=reduce(lambda a,b:b**a, x)
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return x
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def parallel(x): # Parallel resistors [ 1 2 ] => 2/3
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if len(x) == 1:
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return x[0]
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if 0 in x:
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return float('nan')
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x = [1./e for e in x if type(e) == float] # Ignore ^
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return 1./sum(x)
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def sum_parse_action(x): # [ 1 + 2 - 3 ] -> 0
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total = 0.0
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op = ops['+']
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for e in x:
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if e in set('+-'):
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op = ops[e]
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else:
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total=op(total, e)
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return total
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def prod_parse_action(x): # [ 1 * 2 / 3 ] => 0.66
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prod = 1.0
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op = ops['*']
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for e in x:
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if e in set('*/'):
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op = ops[e]
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else:
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prod=op(prod, e)
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return prod
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def func_parse_action(x):
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return [functions[x[0]](x[1])]
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number_suffix=reduce(lambda a,b:a|b, map(Literal,suffixes.keys()), NoMatch()) # SI suffixes and percent
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(dot,minus,plus,times,div,lpar,rpar,exp)=map(Literal,".-+*/()^")
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number_part=Word(nums)
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inner_number = ( number_part+Optional("."+number_part) ) | ("."+number_part) # 0.33 or 7 or .34
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number=Optional(minus | plus)+ inner_number + \
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Optional(CaselessLiteral("E")+Optional("-")+number_part)+ \
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Optional(number_suffix) # 0.33k or -17
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number=number.setParseAction( number_parse_action ) # Convert to number
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# Predefine recursive variables
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expr = Forward()
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factor = Forward()
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def sreduce(f, l):
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''' Same as reduce, but handle len 1 and len 0 lists sensibly '''
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if len(l)==0:
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return NoMatch()
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if len(l)==1:
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return l[0]
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return reduce(f, l)
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# Handle variables passed in. E.g. if we have {'R':0.5}, we make the substitution.
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# Special case for no variables because of how we understand PyParsing is put together
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if len(variables)>0:
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varnames = sreduce(lambda x,y:x|y, map(lambda x: CaselessLiteral(x), variables.keys()))
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varnames.setParseAction(lambda x:map(lambda y:variables[y], x))
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else:
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varnames=NoMatch()
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# Same thing for functions.
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if len(functions)>0:
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funcnames = sreduce(lambda x,y:x|y, map(lambda x: CaselessLiteral(x), functions.keys()))
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function = funcnames+lpar.suppress()+expr+rpar.suppress()
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function.setParseAction(func_parse_action)
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else:
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function = NoMatch()
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atom = number | varnames | lpar+expr+rpar | function
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factor << (atom + ZeroOrMore(exp+atom)).setParseAction(exp_parse_action) # 7^6
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paritem = factor + ZeroOrMore(Literal('||')+factor) # 5k || 4k
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paritem=paritem.setParseAction(parallel)
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term = paritem + ZeroOrMore((times|div)+paritem) # 7 * 5 / 4 - 3
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term = term.setParseAction(prod_parse_action)
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expr << Optional((plus|minus)) + term + ZeroOrMore((plus|minus)+term) # -5 + 4 - 3
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expr=expr.setParseAction(sum_parse_action)
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return (expr+stringEnd).parseString(string)[0]
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if __name__=='__main__':
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variables={'R1':2.0, 'R3':4.0}
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functions={'sin':math.sin, 'cos':math.cos}
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print "X",evaluator(variables, functions, "10000||sin(7+5)-6k")
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print "X",evaluator(variables, functions, "13")
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print evaluator({'R1': 2.0, 'R3':4.0}, {}, "13")
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#
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print evaluator({'a': 2.2997471478310274, 'k': 9, 'm': 8, 'x': 0.66009498411213041}, {}, "5")
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print evaluator({},{}, "-1")
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print evaluator({},{}, "-(7+5)")
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print evaluator({},{}, "-0.33")
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print evaluator({},{}, "-.33")
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print evaluator({},{}, "5+7 QWSEKO")
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