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Add a repeat function to the prelude #18468

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merged 1 commit into from Nov 3, 2014
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7 changes: 6 additions & 1 deletion src/libcore/iter.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2155,7 +2155,7 @@ type IterateState<'a, T> = (|T|: 'a -> T, Option<T>, bool);
/// from a given seed value.
pub type Iterate<'a, T> = Unfold<'a, T, IterateState<'a, T>>;

/// Creates a new iterator that produces an infinite sequence of
/// Create a new iterator that produces an infinite sequence of
/// repeated applications of the given function `f`.
pub fn iterate<'a, T: Clone>(seed: T, f: |T|: 'a -> T) -> Iterate<'a, T> {
Unfold::new((f, Some(seed), true), |st| {
Expand All @@ -2174,6 +2174,11 @@ pub fn iterate<'a, T: Clone>(seed: T, f: |T|: 'a -> T) -> Iterate<'a, T> {
})
}

/// Create a new iterator that endlessly repeats the element `elt`.
pub fn repeat<T: Clone>(elt: T) -> Repeat<T> {
Repeat::new(elt)
}

/// Functions for lexicographical ordering of sequences.
///
/// Lexicographical ordering through `<`, `<=`, `>=`, `>` requires
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2 changes: 1 addition & 1 deletion src/libcore/prelude.rs
Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ pub use option::{Option, Some, None};
pub use result::{Result, Ok, Err};

// Reexported functions
pub use iter::range;
pub use iter::{range, repeat};
pub use mem::drop;

// Reexported types and traits
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8 changes: 8 additions & 0 deletions src/libcoretest/iter.rs
Original file line number Diff line number Diff line change
Expand Up @@ -846,6 +846,14 @@ fn test_iterate() {
assert_eq!(it.next(), Some(8u));
}

#[test]
fn test_repeat() {
let mut it = repeat(42u);
assert_eq!(it.next(), Some(42u));
assert_eq!(it.next(), Some(42u));
assert_eq!(it.next(), Some(42u));
}

#[bench]
fn bench_rposition(b: &mut Bencher) {
let it: Vec<uint> = range(0u, 300).collect();
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2 changes: 1 addition & 1 deletion src/libstd/prelude.rs
Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,7 @@

// Reexported functions
#[doc(no_inline)] pub use from_str::from_str;
#[doc(no_inline)] pub use iter::range;
#[doc(no_inline)] pub use iter::{range, repeat};
#[doc(no_inline)] pub use mem::drop;

// Reexported types and traits
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