fp-ts
Version:
Functional programming in TypeScript
33 lines (32 loc) • 1.43 kB
JavaScript
/**
* A `Foldable` with an additional index.
* A `FoldableWithIndex` instance must be compatible with its `Foldable` instance
*
* ```ts
* reduce(fa, b, f) = reduceWithIndex(fa, b, (_, b, a) => f(b, a))
* foldMap(M)(fa, f) = foldMapWithIndex(M)(fa, (_, a) => f(a))
* reduceRight(fa, b, f) = reduceRightWithIndex(fa, b, (_, a, b) => f(a, b))
* ```
*
* @since 2.0.0
*/
import { getFoldableComposition } from './Foldable';
export function getFoldableWithIndexComposition(F, G) {
var FC = getFoldableComposition(F, G);
return {
reduce: FC.reduce,
foldMap: FC.foldMap,
reduceRight: FC.reduceRight,
reduceWithIndex: function (fga, b, f) {
return F.reduceWithIndex(fga, b, function (fi, b, ga) { return G.reduceWithIndex(ga, b, function (gi, b, a) { return f([fi, gi], b, a); }); });
},
foldMapWithIndex: function (M) {
var foldMapWithIndexF = F.foldMapWithIndex(M);
var foldMapWithIndexG = G.foldMapWithIndex(M);
return function (fga, f) { return foldMapWithIndexF(fga, function (fi, ga) { return foldMapWithIndexG(ga, function (gi, a) { return f([fi, gi], a); }); }); };
},
reduceRightWithIndex: function (fga, b, f) {
return F.reduceRightWithIndex(fga, b, function (fi, ga, b) { return G.reduceRightWithIndex(ga, b, function (gi, a, b) { return f([fi, gi], a, b); }); });
}
};
}