38 lines
809 B
Rust
38 lines
809 B
Rust
trait to_str {
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fn to_str() -> ~str;
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}
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impl of to_str for int {
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fn to_str() -> ~str { int::str(self) }
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}
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impl of to_str for ~str {
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fn to_str() -> ~str { self }
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}
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impl of to_str for () {
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fn to_str() -> ~str { ~"()" }
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}
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trait map<T> {
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fn map<U>(f: fn(T) -> U) -> ~[U];
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}
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impl <T> of map<T> for ~[T] {
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fn map<U>(f: fn(T) -> U) -> ~[U] {
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let mut r = ~[];
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for self.each |x| { r += ~[f(x)]; }
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r
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}
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}
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fn foo<U, T: map<U>>(x: T) -> ~[~str] {
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x.map(|_e| ~"hi" )
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}
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fn bar<U: to_str, T: map<U>>(x: T) -> ~[~str] {
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x.map(|_e| _e.to_str() )
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}
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fn main() {
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assert foo(~[1]) == ~[~"hi"];
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assert bar::<int, ~[int]>(~[4, 5]) == ~[~"4", ~"5"];
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assert bar::<~str, ~[~str]>(~[~"x", ~"y"]) == ~[~"x", ~"y"];
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assert bar::<(), ~[()]>(~[()]) == ~[~"()"];
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}
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