Merge #47

47: Fix is_multiple_of to account for 0 r=cuviper a=WizardOfMenlo

This pull request fixes the implementation to `is_multiple_of` to account for the case in which one of the operand is zero. The current implementation panics, while this one currently concludes that 0 is a multiple of 0 (and in fact the only one).

The change is a minimal check, and an inclusion of this edge case in the tests.

Co-authored-by: Giacomo Fenzi <giacomofenzi@outlook.com>
Co-authored-by: Josh Stone <cuviper@gmail.com>

Cargo.toml

@@ -8,7 +8,7 @@ categories = ["algorithms", "science", "no-std"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-num/num-integer"
 name = "num-integer"
-version = "0.1.44"
+version = "0.1.45"
 readme = "README.md"
 build = "build.rs"
 exclude = ["/bors.toml", "/ci/*", "/.github/*"]

RELEASES.md

@@ -1,3 +1,12 @@
+# Release 0.1.45 (2022-04-29)
+
+- [`Integer::is_multiple_of` now handles a 0 argument without panicking][47]
+  for primitive integers.
+
+**Contributors**: @cuviper, @WizardOfMenlo
+
+[47]: https://github.com/rust-num/num-integer/pull/47
+
 # Release 0.1.44 (2020-10-29)
 
 - [The "i128" feature now bypasses compiler probing][35]. The build script

src/lib.rs

@@ -540,6 +540,9 @@ macro_rules! impl_integer_for_isize {
             /// Returns `true` if the number is a multiple of `other`.
             #[inline]
             fn is_multiple_of(&self, other: &Self) -> bool {
+                if other.is_zero() {
+                    return self.is_zero();
+                }
                 *self % *other == 0
             }
 
@@ -915,6 +918,9 @@ macro_rules! impl_integer_for_usize {
             /// Returns `true` if the number is a multiple of `other`.
             #[inline]
             fn is_multiple_of(&self, other: &Self) -> bool {
+                if other.is_zero() {
+                    return self.is_zero();
+                }
                 *self % *other == 0
             }
 
@@ -1011,9 +1017,14 @@ macro_rules! impl_integer_for_usize {
 
             #[test]
             fn test_is_multiple_of() {
+                assert!((0 as $T).is_multiple_of(&(0 as $T)));
                 assert!((6 as $T).is_multiple_of(&(6 as $T)));
                 assert!((6 as $T).is_multiple_of(&(3 as $T)));
                 assert!((6 as $T).is_multiple_of(&(1 as $T)));
+
+                assert!(!(42 as $T).is_multiple_of(&(5 as $T)));
+                assert!(!(5 as $T).is_multiple_of(&(3 as $T)));
+                assert!(!(42 as $T).is_multiple_of(&(0 as $T)));
             }
 
             #[test]