diff --git a/src/bin/flat/float_fun.rs b/src/bin/flat/float_fun.rs
new file mode 100644
index 0000000..82411e9
--- /dev/null
+++ b/src/bin/flat/float_fun.rs
@@ -0,0 +1,36 @@
+use glam::FloatExt;
+
+mod bounds {
+	pub trait Pair<T> {}
+
+	impl<T> Pair<T> for (T, T) {}
+}
+
+pub trait FloatExt2<T>: bounds::Pair<T> {
+	fn lerp(self, t: T) -> T;
+	fn inverse_lerp(self, y: T) -> T;
+}
+
+impl<F: FloatExt> FloatExt2<F> for (F, F) {
+	fn lerp(self, t: F) -> F { F::lerp(self.0, self.1, t) }
+	fn inverse_lerp(self, y: F) -> F { F::inverse_lerp(self.0, self.1, y) }
+}
+
+#[cfg(test)]
+mod test {
+	use super::FloatExt2;
+
+	#[test]
+	fn test_lerp() {
+		assert_eq!((3., 7.).lerp(-0.5), 1.);
+		assert_eq!((3., 7.).lerp(0.0), 3.);
+		assert_eq!((3., 7.).lerp(0.5), 5.);
+		assert_eq!((3., 7.).lerp(1.0), 7.);
+		assert_eq!((3., 7.).lerp(1.5), 9.);
+		assert_eq!((3., 7.).inverse_lerp(1.), -0.5);
+		assert_eq!((3., 7.).inverse_lerp(3.), 0.0);
+		assert_eq!((3., 7.).inverse_lerp(5.), 0.5);
+		assert_eq!((3., 7.).inverse_lerp(7.), 1.0);
+		assert_eq!((3., 7.).inverse_lerp(9.), 1.5);
+	}
+}
diff --git a/src/bin/flat/fns.rs b/src/bin/flat/fns.rs
index c6d94d8..526e6d7 100644
--- a/src/bin/flat/fns.rs
+++ b/src/bin/flat/fns.rs
@@ -1,4 +1,4 @@
-use crate::FloatExt2;
+use crate::float_fun::FloatExt2;
 
 pub struct LinearLimiter {
 	pub min: f32,
diff --git a/src/bin/flat/main.rs b/src/bin/flat/main.rs
index 244b2f7..2f65d2a 100644
--- a/src/bin/flat/main.rs
+++ b/src/bin/flat/main.rs
@@ -5,6 +5,7 @@ use glam::*;
 
 mod riemann;
 mod fns;
+mod float_fun;
 
 use riemann::{Tens2, Decomp2, Metric, trace_iter};
 use shape::Shape;
@@ -680,13 +681,3 @@ fn test_tube_metric_derivs() {
 		}
 	}
 }
-
-trait FloatExt2 {
-	fn lerp(&self, t: f32) -> f32;
-	fn inverse_lerp(&self, y: f32) -> f32;
-}
-
-impl FloatExt2 for (f32, f32) {
-	fn lerp(&self, t: f32) -> f32 { f32::lerp(self.0, self.1, t) }
-	fn inverse_lerp(&self, y: f32) -> f32 { f32::inverse_lerp(self.0, self.1, y) }
-}