sign directly after * cause crash

[owarnier]

This expression perse without problem
parser.parse('-2*3').evaluate({})

This expression crash
parser.parse('2*-3').evaluate({})

---

_IndexError Traceback (most recent call last)
in
----> 1 parser.parse('2*-3').evaluate({})

~/Library/Python/3.7/lib/python/site-packages/py_expression_eval/init.py in evaluate(self, values)
118 elif type_ == TOP2:
119 n2 = nstack.pop()
--> 120 n1 = nstack.pop()
121 f = self.ops2[item.index_]
122 nstack.append(f(n1, n2))

IndexError: pop from empty list_

eval('2*-3') works on python3.7

[owarnier]

version
py-expression-eval 0.3.14

[kcrossen]

Leading minus sign in context where subtraction makes no sense (would be a grammar error) should have the highest priority. Otherwise, there will be a (R-associative) negation operator left at the end of the dance with no dance partner.
change py_expression_eval/init.py line 455 from:
self.tokenprio = 5
to:
self.tokenprio = 10
currently::
while self.pos < len(self.expression): if self.isOperator(): if self.isSign() and expected & self.SIGN: if self.isNegativeSign(): self.tokenprio = 5 self.tokenindex = '-' noperators += 1 self.addfunc(tokenstack, operstack, TOP1)
change to:
while self.pos < len(self.expression): if self.isOperator(): if self.isSign() and expected & self.SIGN: if self.isNegativeSign(): self.tokenprio = 10 self.tokenindex = '-' noperators += 1 self.addfunc(tokenstack, operstack, TOP1)