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Simplify slice's first(_mut) and last(_mut) with get #54422

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Merged
merged 1 commit into from
Sep 22, 2018
Merged

Simplify slice's first(_mut) and last(_mut) with get #54422

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12 changes: 6 additions & 6 deletions src/libcore/slice/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -119,7 +119,7 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn first(&self) -> Option<&T> {
if self.is_empty() { None } else { Some(&self[0]) }
self.get(0)
}

/// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
Expand All @@ -137,7 +137,7 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn first_mut(&mut self) -> Option<&mut T> {
if self.is_empty() { None } else { Some(&mut self[0]) }
self.get_mut(0)
}

/// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
Expand Down Expand Up @@ -239,7 +239,8 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn last(&self) -> Option<&T> {
if self.is_empty() { None } else { Some(&self[self.len() - 1]) }
let last_idx = self.len().checked_sub(1)?;
self.get(last_idx)
}

/// Returns a mutable pointer to the last item in the slice.
Expand All @@ -257,9 +258,8 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn last_mut(&mut self) -> Option<&mut T> {
let len = self.len();
if len == 0 { return None; }
Some(&mut self[len - 1])
let last_idx = self.len().checked_sub(1)?;
self.get_mut(last_idx)
}

/// Returns a reference to an element or subslice depending on the type of
Expand Down