correct fixnum overflow on negation (#528)

2020-05-19 10:45:54 -06:00
parent e0e3b180e7
commit 2eac902c33
1 changed files with 6 additions and 1 deletions
--- a/src/prolog/arithmetic.rs
+++ b/src/prolog/arithmetic.rs
@@ -474,7 +474,12 @@ impl Neg for Number {

    fn neg(self) -> Self::Output {
        match self {
-            Number::Fixnum(n) => Number::Fixnum(-n),
+            Number::Fixnum(n) =>
+                if let Some(n) = n.checked_neg() {
+                    Number::Fixnum(n)
+                } else {
+                    Number::from(-Integer::from(n))
+                }
            Number::Integer(n) => Number::Integer(Rc::new(-Integer::from(&*n))),
            Number::Float(OrderedFloat(f)) => Number::Float(OrderedFloat(-f)),
            Number::Rational(r) => Number::Rational(Rc::new(-Rational::from(&*r))),