83 lines
2.1 KiB
Rust
83 lines
2.1 KiB
Rust
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// A trait for objects that can be used to do an if-then-else
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// (No actual need for this to be static, but it is a simple test.)
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trait bool_like {
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static fn select<A>(b: self, +x1: A, +x2: A) -> A;
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}
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fn andand<T: bool_like Copy>(x1: T, x2: T) -> T {
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select(x1, x2, x1)
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}
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impl bool: bool_like {
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static fn select<A>(&&b: bool, +x1: A, +x2: A) -> A {
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if b { x1 } else { x2 }
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}
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}
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impl int: bool_like {
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static fn select<A>(&&b: int, +x1: A, +x2: A) -> A {
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if b != 0 { x1 } else { x2 }
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}
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}
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// A trait for sequences that can be constructed imperatively.
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trait buildable<A> {
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static pure fn build_sized(size: uint,
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builder: fn(push: pure fn(+A))) -> self;
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}
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impl<A> @[A]: buildable<A> {
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#[inline(always)]
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static pure fn build_sized(size: uint,
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builder: fn(push: pure fn(+A))) -> @[A] {
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at_vec::build_sized(size, builder)
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}
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}
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impl<A> ~[A]: buildable<A> {
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#[inline(always)]
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static pure fn build_sized(size: uint,
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builder: fn(push: pure fn(+A))) -> ~[A] {
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vec::build_sized(size, builder)
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}
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}
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#[inline(always)]
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pure fn build<A, B: buildable<A>>(builder: fn(push: pure fn(+A))) -> B {
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build_sized(4, builder)
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}
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/// Apply a function to each element of an iterable and return the results
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fn map<T, IT: BaseIter<T>, U, BU: buildable<U>>
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(v: IT, f: fn(T) -> U) -> BU {
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do build |push| {
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for v.each() |elem| {
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push(f(elem));
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}
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}
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}
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fn seq_range<BT: buildable<int>>(lo: uint, hi: uint) -> BT {
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do build_sized(hi-lo) |push| {
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for uint::range(lo, hi) |i| {
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push(i as int);
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}
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}
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}
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fn main() {
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let v: @[int] = seq_range(0, 10);
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assert v == @[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
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let v: @[int] = map(&[1,2,3], |x| 1+x);
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assert v == @[2, 3, 4];
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let v: ~[int] = map(&[1,2,3], |x| 1+x);
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assert v == ~[2, 3, 4];
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assert select(true, 9, 14) == 9;
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assert !andand(true, false);
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assert andand(7, 12) == 12;
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assert andand(0, 12) == 0;
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}
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