laundmo · December 28, 2023 14:47 · Dec 28, 2023
diff --git a/lerp.rs b/lerp.rs
@@ -0,0 +1,32 @@
+trait Lerp<T> {
+    fn lerp(self, from: T, to: T) -> T;
+    fn inv_lerp(self, from: T, to: T) -> T;
+    fn remap(self, from_range: (T, T), to_range: (T, T)) -> T;
+}
+
+macro_rules! lerp_impl {
+    ($one:literal, $typ:ty) => {
+        impl Lerp<$typ> for $typ {
+            #[inline(always)]
+            fn lerp(self, from: $typ, to: $typ) -> $typ {
+                //! Linear interpolate on the scale given by a to b, using t as the point on that scale.
+                ($one - self) * from + self * to
+            }
+            #[inline(always)]
+            fn inv_lerp(self, from: $typ, to: $typ) -> $typ {
+                //! Inverse Linar Interpolation, get the fraction between a and b on which v resides.
+                (self - from) / (to - from)
+            }
+            #[inline(always)]
+            fn remap(self, from_range: ($typ, $typ), to_range: ($typ, $typ)) -> $typ {
+                //! Remap values from one linear scale to another, a combination of lerp and inv_lerp.
+                //! i_range is the scale of the original value,
+                //! o_range is the scale of the resulting value.
+                self.inv_lerp(from_range.0, from_range.1)
+                    .lerp(to_range.0, to_range.1)
+            }
+        }
+    };
+}
+lerp_impl!(1., f32);
+lerp_impl!(1., f64);