Merge pull request #4 from cuviper/super-float-to-int

Make `PrimitiveFloatToInt` a supertrait of `PrimitiveFloat`

Author: cuviper

.gitignore

@@ -1 +1,2 @@
+/Cargo.lock
 /target

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "num-primitive"
-version = "0.1.1"
+version = "0.2.0"
 description = "Traits for primitive numeric types"
 repository = "https://github.com/rust-num/num-primitive"
 license = "MIT OR Apache-2.0"

Cargo.toml

@@ -54,7 +54,22 @@ struct SealedToken;
 /// assert_eq!(distance_squared::<f64>(&[0., 1., 2.], &[1., 3., 0.]), 9.);
 /// ```
 pub trait PrimitiveFloat:
-    PrimitiveNumber + From<i8> + From<u8> + core::ops::Neg<Output = Self>
+    PrimitiveNumber
+    + PrimitiveFloatToInt<i8>
+    + PrimitiveFloatToInt<i16>
+    + PrimitiveFloatToInt<i32>
+    + PrimitiveFloatToInt<i64>
+    + PrimitiveFloatToInt<i128>
+    + PrimitiveFloatToInt<isize>
+    + PrimitiveFloatToInt<u8>
+    + PrimitiveFloatToInt<u16>
+    + PrimitiveFloatToInt<u32>
+    + PrimitiveFloatToInt<u64>
+    + PrimitiveFloatToInt<u128>
+    + PrimitiveFloatToInt<usize>
+    + core::convert::From<i8>
+    + core::convert::From<u8>
+    + core::ops::Neg<Output = Self>
 {
     /// Approximate number of significant digits in base 10.
     const DIGITS: u32;
@@ -405,7 +420,42 @@ pub trait PrimitiveFloatRef<T>: PrimitiveNumberRef<T> + core::ops::Neg<Output =
 ///
 /// This is effectively the same as the unstable [`core::convert::FloatToInt`], implemented for all
 /// combinations of [`PrimitiveFloat`] and [`PrimitiveInteger`][crate::PrimitiveInteger].
-pub trait PrimitiveFloatToInt<Int>: PrimitiveFloat {
+///
+/// # Examples
+///
+/// `PrimitiveFloatToInt<{integer}>` is a supertrait of [`PrimitiveFloat`] for all primitive
+/// integers, so you do not need to use this trait directly with concrete integer types.
+///
+/// ```
+/// use num_primitive::PrimitiveFloat;
+///
+/// fn pi<Float: PrimitiveFloat>() -> i32 {
+///     // SAFETY: π is finite, and truncated to 3 fits any int
+///     unsafe { Float::PI.to_int_unchecked() }
+/// }
+///
+/// assert_eq!(pi::<f32>(), 3i32);
+/// assert_eq!(pi::<f64>(), 3i32);
+/// ```
+///
+/// However, if the integer type is also generic, an explicit type constraint is needed.
+///
+/// ```
+/// use num_primitive::{PrimitiveFloat, PrimitiveFloatToInt};
+///
+/// fn tau<Float, Int>() -> Int
+/// where
+///     Float: PrimitiveFloat + PrimitiveFloatToInt<Int>,
+/// {
+///     // SAFETY: τ is finite, and truncated to 6 fits any int
+///     unsafe { Float::TAU.to_int_unchecked() }
+/// }
+///
+/// assert_eq!(tau::<f32, i64>(), 6i64);
+/// assert_eq!(tau::<f64, u8>(), 6u8);
+/// ```
+///
+pub trait PrimitiveFloatToInt<Int> {
     #[doc(hidden)]
     #[expect(private_interfaces)]
     unsafe fn __to_int_unchecked(x: Self, _: SealedToken) -> Int;

src/float.rs

@@ -17,7 +17,7 @@ extern crate alloc;
 use alloc::boxed::Box;
 use core::error::Error;
 
-use crate::{PrimitiveError, PrimitiveFloatToInt, PrimitiveInteger, PrimitiveNumber};
+use crate::{PrimitiveError, PrimitiveInteger, PrimitiveNumber};
 
 fn check_result<'a, T: PrimitiveNumber, E: PrimitiveError>(r: Result<T, E>, ok: T) {
     // Cloning and equating results requires `E: Clone + PartialEq`
@@ -58,13 +58,3 @@ fn try_into() {
     }
     check(0i32, 0u32);
 }
-
-#[test]
-fn to_int_unchecked() {
-    fn pi<T: PrimitiveFloatToInt<Int>, Int>() -> Int {
-        // SAFETY: π is finite, and truncated to 3 fits any int
-        unsafe { T::PI.to_int_unchecked() }
-    }
-    assert_eq!(pi::<f32, i64>(), 3i64);
-    assert_eq!(pi::<f64, u8>(), 3u8);
-}