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Correct and clarify integer division rounding docs #26981

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Jul 13, 2015
Merged

Correct and clarify integer division rounding docs #26981

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218eb12
Correct and clarify integer division rounding docs
wthrowe Jul 12, 2015
7824956
Move rounding discussion to integer Div/Rem impls
wthrowe Jul 13, 2015
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8 changes: 4 additions & 4 deletions src/libcore/num/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -459,15 +459,15 @@ macro_rules! int_impl {
}
}

/// Wrapping (modular) division. Computes `floor(self / other)`,
/// Wrapping (modular) division. Computes `self / other`,
/// wrapping around at the boundary of the type.
///
/// The only case where such wrapping can occur is when one
/// divides `MIN / -1` on a signed type (where `MIN` is the
/// negative minimal value for the type); this is equivalent
/// to `-MIN`, a positive value that is too large to represent
/// in the type. In such a case, this function returns `MIN`
/// itself..
/// itself.
#[stable(feature = "num_wrapping", since = "1.2.0")]
#[inline(always)]
pub fn wrapping_div(self, rhs: Self) -> Self {
Expand Down Expand Up @@ -1031,15 +1031,15 @@ macro_rules! uint_impl {
}
}

/// Wrapping (modular) division. Computes `floor(self / other)`,
/// Wrapping (modular) division. Computes `self / other`,
/// wrapping around at the boundary of the type.
///
/// The only case where such wrapping can occur is when one
/// divides `MIN / -1` on a signed type (where `MIN` is the
/// negative minimal value for the type); this is equivalent
/// to `-MIN`, a positive value that is too large to represent
/// in the type. In such a case, this function returns `MIN`
/// itself..
/// itself.
#[stable(feature = "num_wrapping", since = "1.2.0")]
#[inline(always)]
pub fn wrapping_div(self, rhs: Self) -> Self {
Expand Down
24 changes: 22 additions & 2 deletions src/libcore/ops.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -351,8 +351,10 @@ pub trait Div<RHS=Self> {
fn div(self, rhs: RHS) -> Self::Output;
}

macro_rules! div_impl {
macro_rules! div_impl_integer {
($($t:ty)*) => ($(
/// This operation rounds towards zero, truncating any
/// fractional part of the exact result.
#[stable(feature = "rust1", since = "1.0.0")]
impl Div for $t {
type Output = $t;
Expand All @@ -365,7 +367,23 @@ macro_rules! div_impl {
)*)
}

div_impl! { usize u8 u16 u32 u64 isize i8 i16 i32 i64 f32 f64 }
div_impl_integer! { usize u8 u16 u32 u64 isize i8 i16 i32 i64 }

macro_rules! div_impl_float {
($($t:ty)*) => ($(
#[stable(feature = "rust1", since = "1.0.0")]
impl Div for $t {
type Output = $t;

#[inline]
fn div(self, other: $t) -> $t { self / other }
}

forward_ref_binop! { impl Div, div for $t, $t }
)*)
}

div_impl_float! { f32 f64 }

/// The `Rem` trait is used to specify the functionality of `%`.
///
Expand Down Expand Up @@ -407,6 +425,8 @@ pub trait Rem<RHS=Self> {

macro_rules! rem_impl {
($($t:ty)*) => ($(
/// This operation satisfies `n % d == n - (n / d) * d`. The
/// result has the same sign as the left operand.
#[stable(feature = "rust1", since = "1.0.0")]
impl Rem for $t {
type Output = $t;
Expand Down