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Added documentation on the remainder (Rem) operator for floating points. #59529

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Merged
merged 3 commits into from
Apr 2, 2019
Merged

Added documentation on the remainder (Rem) operator for floating points. #59529

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8fe1087
Added documentation on the remainder (Rem) operator for floating points.
Mar 29, 2019
ea369cb
Added an example that shows how the remainder function on floating po…
Mar 30, 2019
a1c7905
Improved the example with numbers that can be exactly represented as …
Apr 1, 2019
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15 changes: 15 additions & 0 deletions src/libcore/ops/arith.rs
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Expand Up @@ -537,6 +537,21 @@ rem_impl_integer! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }

macro_rules! rem_impl_float {
($($t:ty)*) => ($(

/// The remainder from the division of two floats.
///
/// The remainder has the same sign as the dividend and is computed as:
/// `x - (x / y).trunc() * y`.
///
/// # Examples
/// ```
/// let x: f32 = 50.50;
/// let y: f32 = 8.125;
/// let remainder = x - (x / y).trunc() * y;
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@cuviper cuviper Apr 1, 2019

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I'd comment the expected value (1.5) for demonstration purposes. Might be nicer to choose inputs with a greater quotient too, so this doesn't look like just subtraction.
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@DevQps DevQps Apr 1, 2019

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Alright! So what about 15.2 and 2.3? (Just some random numbers). Then I would also add a comment that the result is: 1.4
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@cuviper cuviper Apr 1, 2019

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Random is fine, but maybe stick to base-2 numbers that float can represent exactly.
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@DevQps DevQps Apr 1, 2019

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@cuviper I updated the example! What about this?
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@cuviper cuviper Apr 2, 2019

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Works for me!
///
/// // The answer to both operations is 1.75
/// assert_eq!(x % y, remainder);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
impl Rem for $t {
type Output = $t;
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