58 lines
1.4 KiB
TypeScript
58 lines
1.4 KiB
TypeScript
// compose :: (b->c) -> (a->b) -> (a->c)
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function compose<A, B, C>(f: (b: B) => C, g: (a:A) => B): (a:A) => C {
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return function (a:A) : C {
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return f(g.apply(null, a));
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};
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}
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// forEach :: [a] -> (a -> ()) -> ()
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function forEach<A>(list: A[], f: (a: A, n?: number) => void ): void {
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for (var i = 0; i < list.length; ++i) {
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f(list[i], i);
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}
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}
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// filter :: (a->bool) -> [a] -> [a]
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function filter<A>(f: (a: A) => boolean, ar: A[]): A[] {
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var ret = [];
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forEach(ar, (el) => {
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if (f(el)) {
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ret.push(el);
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}
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} );
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return ret;
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}
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// length :: [a] -> Num
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function length2<A>(ar: A[]): number {
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return ar.length;
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}
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// curry1 :: ((a,b)->c) -> (a->(b->c))
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function curry1<A, B, C>(f: (a: A, b: B) => C): (ax: A) => (bx: B) => C {
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return function (ay: A) {
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return function (by: B) {
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return f(ay, by);
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};
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};
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}
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var cfilter = curry1(filter);
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// compose :: (b->c) -> (a->b) -> (a->c)
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// length :: [a] -> Num
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// cfilter :: {} -> {} -> [{}]
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// pred :: a -> Bool
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// cfilter(pred) :: {} -> [{}]
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// length2 :: [a] -> Num
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// countWhere :: (a -> Bool) -> [a] -> Num
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function countWhere_1<A>(pred: (a: A) => boolean): (a: A[]) => number {
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return compose(length2, cfilter(pred));
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}
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function countWhere_2<A>(pred: (a: A) => boolean): (a: A[]) => number {
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var where = cfilter(pred);
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return compose(length2, where);
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} |