More lerp tests, altering lerp docs

[rust.git] / library / std / src / f32 / tests.rs

diff --git a/library/std/src/f32/tests.rs b/library/std/src/f32/tests.rs
index 0d4b865f3392a66304e13e47e9fa652099428534..fe66a73afd63ab7ef6d55f5dfe708640e22cde46 100644 (file)
--- a/library/std/src/f32/tests.rs
+++ b/library/std/src/f32/tests.rs
@@ -757,3 +757,66 @@ fn s_nan() -> f32 {
     assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&f32::INFINITY));
     assert_eq!(Ordering::Less, (-s_nan()).total_cmp(&s_nan()));
 }
+
+#[test]
+fn test_lerp_exact() {
+    // simple values
+    assert_eq!(f32::lerp(0.0, 2.0, 4.0), 2.0);
+    assert_eq!(f32::lerp(1.0, 2.0, 4.0), 4.0);
+
+    // boundary values
+    assert_eq!(f32::lerp(0.0, f32::MIN, f32::MAX), f32::MIN);
+    assert_eq!(f32::lerp(1.0, f32::MIN, f32::MAX), f32::MAX);
+}
+
+#[test]
+fn test_lerp_consistent() {
+    assert_eq!(f32::lerp(f32::MAX, f32::MIN, f32::MIN), f32::MIN);
+    assert_eq!(f32::lerp(f32::MIN, f32::MAX, f32::MAX), f32::MAX);
+
+    // as long as t is finite, a/b can be infinite
+    assert_eq!(f32::lerp(f32::MAX, f32::NEG_INFINITY, f32::NEG_INFINITY), f32::NEG_INFINITY);
+    assert_eq!(f32::lerp(f32::MIN, f32::INFINITY, f32::INFINITY), f32::INFINITY);
+}
+
+#[test]
+fn test_lerp_nan_infinite() {
+    // non-finite t is not NaN if a/b different
+    assert!(!f32::lerp(f32::INFINITY, f32::MIN, f32::MAX).is_nan());
+    assert!(!f32::lerp(f32::NEG_INFINITY, f32::MIN, f32::MAX).is_nan());
+}
+
+#[test]
+fn test_lerp_values() {
+    // just a few basic values
+    assert_eq!(f32::lerp(0.25, 1.0, 2.0), 1.25);
+    assert_eq!(f32::lerp(0.50, 1.0, 2.0), 1.50);
+    assert_eq!(f32::lerp(0.75, 1.0, 2.0), 1.75);
+}
+
+#[test]
+fn test_lerp_monotonic() {
+    // near 0
+    let below_zero = f32::lerp(-f32::EPSILON, f32::MIN, f32::MAX);
+    let zero = f32::lerp(0.0, f32::MIN, f32::MAX);
+    let above_zero = f32::lerp(f32::EPSILON, f32::MIN, f32::MAX);
+    assert!(below_zero <= zero);
+    assert!(zero <= above_zero);
+    assert!(below_zero <= above_zero);
+
+    // near 0.5
+    let below_half = f32::lerp(0.5 - f32::EPSILON, f32::MIN, f32::MAX);
+    let half = f32::lerp(0.5, f32::MIN, f32::MAX);
+    let above_half = f32::lerp(0.5 + f32::EPSILON, f32::MIN, f32::MAX);
+    assert!(below_half <= half);
+    assert!(half <= above_half);
+    assert!(below_half <= above_half);
+
+    // near 1
+    let below_one = f32::lerp(1.0 - f32::EPSILON, f32::MIN, f32::MAX);
+    let one = f32::lerp(1.0, f32::MIN, f32::MAX);
+    let above_one = f32::lerp(1.0 + f32::EPSILON, f32::MIN, f32::MAX);
+    assert!(below_one <= one);
+    assert!(one <= above_one);
+    assert!(below_one <= above_one);
+}