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core: convert vec::{head,head_opt} to return references

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This commit is contained in:
Erick Tryzelaar 2013-03-02 21:49:50 -08:00
parent 431e756fd7
commit 359bb3e10b
6 changed files with 68 additions and 31 deletions
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52
src/libcore/vec.rs
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@ -211,7 +211,16 @@ pub pure fn build_sized_opt<A>(size: Option<uint>,
// Accessors
/// Returns the first element of a vector
pub pure fn head<T:Copy>(v: &[const T]) -> T { v[0] }
pub pure fn head<T>(v: &r/[T]) -> &r/T {
if v.len() == 0 { fail!(~"last_unsafe: empty vector") }
&v[0]
}
/// Returns `Some(x)` where `x` is the first element of the slice `v`,
/// or `None` if the vector is empty.
pub pure fn head_opt<T>(v: &r/[T]) -> Option<&r/T> {
if v.len() == 0 { None } else { Some(&v[0]) }
}
/// Returns a vector containing all but the first element of a slice
pub pure fn tail<T:Copy>(v: &[const T]) -> ~[T] {
@ -1692,7 +1701,6 @@ impl<T> Container for &[const T] {
}
pub trait CopyableVector<T> {
pure fn head(&self) -> T;
pure fn init(&self) -> ~[T];
pure fn last(&self) -> T;
pure fn slice(&self, start: uint, end: uint) -> ~[T];
@ -1701,10 +1709,6 @@ pub trait CopyableVector<T> {
/// Extension methods for vectors
impl<T:Copy> CopyableVector<T> for &[const T] {
/// Returns the first element of a vector
#[inline]
pure fn head(&self) -> T { head(*self) }
/// Returns all but the last elemnt of a vector
#[inline]
pure fn init(&self) -> ~[T] { init(*self) }
@ -1726,7 +1730,9 @@ impl<T:Copy> CopyableVector<T> for &[const T] {
pub trait ImmutableVector<T> {
pure fn view(&self, start: uint, end: uint) -> &self/[T];
pure fn foldr<U:Copy>(&self, z: U, p: fn(t: &T, u: U) -> U) -> U;
pure fn head(&self) -> &self/T;
pure fn head_opt(&self) -> Option<&self/T>;
pure fn foldr<U: Copy>(&self, z: U, p: fn(t: &T, u: U) -> U) -> U;
pure fn map<U>(&self, f: fn(t: &T) -> U) -> ~[U];
pure fn mapi<U>(&self, f: fn(uint, t: &T) -> U) -> ~[U];
fn map_r<U>(&self, f: fn(x: &T) -> U) -> ~[U];
@ -1743,6 +1749,14 @@ impl<T> ImmutableVector<T> for &[T] {
slice(*self, start, end)
}
/// Returns the first element of a vector, failing if the vector is empty.
#[inline]
pure fn head(&self) -> &self/T { head(*self) }
/// Returns the first element of a vector
#[inline]
pure fn head_opt(&self) -> Option<&self/T> { head_opt(*self) }
/// Reduce a vector from right to left
#[inline]
pure fn foldr<U:Copy>(&self, z: U, p: fn(t: &T, u: U) -> U) -> U {
@ -2570,8 +2584,28 @@ mod tests {
#[test]
fn test_head() {
let a = ~[11, 12];
assert (head(a) == 11);
let mut a = ~[11];
assert a.head() == &11;
a = ~[11, 12];
assert a.head() == &11;
}
#[test]
#[should_fail]
#[ignore(cfg(windows))]
fn test_head_empty() {
let a: ~[int] = ~[];
a.head();
}
#[test]
fn test_head_opt() {
let mut a = ~[];
assert a.head_opt() == None;
a = ~[11];
assert a.head_opt().unwrap() == &11;
a = ~[11, 12];
assert a.head_opt().unwrap() == &11;
}
#[test]