Expressions need a space around everything. e.g. "i and ( j or k )" not "i and (j or k)"
Created
February 20, 2012 03:13
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Python boolean statement to RPN
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parse("( S < 16 and T = \"P\" ) or ( S > 16 and L = 50 )") => ['S<16', 'T="P"', 'and', 'S>16', 'L=50', 'and', 'or'] |
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def parse(statement): | |
arg = "" | |
stack = [] | |
output = [""] | |
consume = False | |
ops = ["and", "or"] | |
for g in statement.split(" "): | |
slashquote = (len(g) - len(g.replace("\\\"","")))/2 | |
quote = (len(g) - len(g.replace("\"","")))-slashquote | |
if quote % 2 == 1: | |
consume = not consume | |
if not consume: | |
if g in ops: | |
while len(stack) > 0 and stack[0] in ops: | |
output = output + [stack.pop(0)] | |
output = output + [""] | |
stack = [g] + stack | |
elif g == "(": | |
stack = [g] + stack | |
elif g == ")": | |
while stack[0] != "(": | |
temp = stack.pop(0) | |
if len(stack) == 0: | |
print "Error Line", i - 1, "Unmatched parenteses" | |
return None | |
output = output + [temp] | |
stack.pop(0) | |
else: | |
#combine everything else into a single token ("i" ">" "16" -> "i>16") | |
output[-1] = output[-1] + g | |
else: | |
output[-1] = output[-1] + " " + g | |
while len(stack) > 0: | |
output = output + [stack.pop(0)] | |
return output |
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