add tests

Author: tgross35

src/math/generic/scalbn.rs

@@ -81,3 +81,57 @@ where
 
     x * F::from_bits(F::Int::cast_from(F::EXP_BIAS as i32 + n) << F::SIG_BITS)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::super::super::Int;
+    use super::*;
+
+    // Tests against N3220
+    fn spec_test<F: Float>()
+    where
+        u32: CastInto<F::Int>,
+        F::Int: CastFrom<i32>,
+        F::Int: CastFrom<u32>,
+    {
+        // `scalbn(±0, n)` returns `±0`.
+        assert_biteq!(scalbn(F::NEG_ZERO, 10), F::NEG_ZERO);
+        assert_biteq!(scalbn(F::NEG_ZERO, 0), F::NEG_ZERO);
+        assert_biteq!(scalbn(F::NEG_ZERO, -10), F::NEG_ZERO);
+        assert_biteq!(scalbn(F::ZERO, 10), F::ZERO);
+        assert_biteq!(scalbn(F::ZERO, 0), F::ZERO);
+        assert_biteq!(scalbn(F::ZERO, -10), F::ZERO);
+
+        // `scalbn(x, 0)` returns `x`.
+        assert_biteq!(scalbn(F::MIN, 0), F::MIN);
+        assert_biteq!(scalbn(F::MAX, 0), F::MAX);
+        assert_biteq!(scalbn(F::INFINITY, 0), F::INFINITY);
+        assert_biteq!(scalbn(F::NEG_INFINITY, 0), F::NEG_INFINITY);
+        assert_biteq!(scalbn(F::ZERO, 0), F::ZERO);
+        assert_biteq!(scalbn(F::NEG_ZERO, 0), F::NEG_ZERO);
+
+        // `scalbn(±∞, n)` returns `±∞`.
+        assert_biteq!(scalbn(F::INFINITY, 10), F::INFINITY);
+        assert_biteq!(scalbn(F::INFINITY, -10), F::INFINITY);
+        assert_biteq!(scalbn(F::NEG_INFINITY, 10), F::NEG_INFINITY);
+        assert_biteq!(scalbn(F::NEG_INFINITY, -10), F::NEG_INFINITY);
+
+        // NaN should return unchanged
+        assert_biteq!(scalbn(F::NAN, 10), F::NAN);
+        assert_biteq!(scalbn(F::NAN, 0), F::NAN);
+        assert_biteq!(scalbn(F::NAN, -10), F::NAN);
+        assert_biteq!(scalbn(-F::NAN, 10), -F::NAN);
+        assert_biteq!(scalbn(-F::NAN, 0), -F::NAN);
+        assert_biteq!(scalbn(-F::NAN, -10), -F::NAN);
+    }
+
+    #[test]
+    fn spec_test_f32() {
+        spec_test::<f32>();
+    }
+
+    #[test]
+    fn spec_test_f64() {
+        spec_test::<f64>();
+    }
+}