Add lossy conversion for NotNan<f64> to NotNan<f32> (#109)

Author: MultisampledNight

src/lib.rs

@@ -954,6 +954,18 @@ impl<T: Float + fmt::Display> fmt::Display for NotNan<T> {
     }
 }
 
+impl NotNan<f64> {
+    /// Converts this [`NotNan`]`<`[`f64`]`>` to a [`NotNan`]`<`[`f32`]`>` while giving up on
+    /// precision, [using `roundTiesToEven` as rounding mode, yielding `Infinity` on
+    /// overflow](https://doc.rust-lang.org/reference/expressions/operator-expr.html#semantics).
+    pub fn as_f32(self) -> NotNan<f32> {
+        // This is not destroying invariants, as it is a pure rounding operation. The only two special
+        // cases are where f32 would be overflowing, then the operation yields Infinity, or where
+        // the input is already NaN, in which case the invariant is already broken elsewhere.
+        NotNan(self.0 as f32)
+    }
+}
+
 impl From<NotNan<f32>> for f32 {
     #[inline]
     fn from(value: NotNan<f32>) -> Self {