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reduce.ts
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reduce.ts
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// Copyright (c) 2020 Jozty. All rights reserved. MIT license.
import { isArrayLike, isIterable, isIterator } from './utils/is.ts';
import { getIterator, getTransformer } from './utils/get.ts';
import curryN from './utils/curry_n.ts';
import type { FuncArr2, FunctorWithArLk, PH } from './utils/types.ts';
import Transformer, {
ReducedTransformer,
} from './utils/Transformers/transformers.ts';
import { throwFunctorError } from './utils/throw.ts';
// @types
type Reducer<R, P> =
| FuncArr2<R, P, R | ReducedTransformer<R>>
| Transformer;
type Reduce_1<T, R> = <P>(func: Reducer<R, P>) => R;
type Reduce_2<T, R, P> = (acc: R) => R;
type Reduce_3<R, P> = <T>(functor: FunctorWithArLk<T>) => R;
type Reduce_2_3<R, P> =
& ((acc: R) => Reduce_3<R, P>)
& (<T>(acc: PH, functor: FunctorWithArLk<T>) => Reduce_2<T, R, P>)
& (<T>(acc: R, functor: FunctorWithArLk<T>) => R);
type Reduce_1_3<R> =
& (<P>(func: Reducer<R, P>) => Reduce_3<R, P>)
& (<T>(func: PH, functor: FunctorWithArLk<T>) => Reduce_1<T, R>)
& (<T, P>(func: Reducer<R, P>, functor: FunctorWithArLk<T>) => R);
type Reduce_1_2<T> =
& (<R, P>(func: Reducer<R, P>) => Reduce_2<T, R, P>)
& (<R>(func: PH, acc: R) => Reduce_1<T, R>)
& (<R, P>(func: Reducer<R, P>, acc: R) => R);
type Reduce =
& (<R, P>(func: Reducer<R, P>) => Reduce_2_3<R, P>)
& (<R>(func: PH, acc: R) => Reduce_1_3<R>)
& (<T>(func: PH, acc: PH, functor: FunctorWithArLk<T>) => Reduce_1_2<T>)
& (<R, P>(func: Reducer<R, P>, acc: R) => Reduce_3<R, P>)
& (<T, R, P>(
func: Reducer<R, P>,
acc: PH,
functor: FunctorWithArLk<T>,
) => Reduce_2<T, R, P>)
& (<T, R>(func: PH, acc: R, functor: FunctorWithArLk<T>) => Reduce_1<T, R>)
& (<T, R, P>(func: Reducer<R, P>, acc: R, functor: FunctorWithArLk<T>) => R);
function _arrayReduce<T, R>(
trans: Transformer,
acc: R,
list: ArrayLike<T>,
): R {
for (let i = 0, l = list.length; i < l; i++) {
acc = trans.step(acc, list[i]);
if (acc && acc instanceof ReducedTransformer) {
acc = acc.value;
break;
}
}
return trans.result(acc);
}
function _iterableReduce<T, R>(
trans: Transformer,
acc: R,
it: Iterator<T>,
): R {
let step = it.next();
while (!step.done) {
acc = trans.step(acc, step.value);
if (acc && acc instanceof ReducedTransformer) {
acc = acc.value;
break;
}
step = it.next();
}
return trans.result(acc);
}
function _reduce<T, R, P>(
func: Reducer<R, P>,
acc: R,
functor: FunctorWithArLk<T>,
): R {
let trans = getTransformer(func);
if (isArrayLike(functor)) return _arrayReduce(trans, acc, functor);
if (isIterable(functor)) {
return _iterableReduce(trans, acc, getIterator<T>(functor));
}
if (isIterator(functor)) return _iterableReduce(trans, acc, functor);
throwFunctorError();
}
/**
* Returns a single value by iterating though `functor`
* calling the iterator function `func`. `func` takes two arguments.
* First - `acc`, Second - `value`.
*
* It may stop the reduction in between by means of `ReducedTransformer`.
*
* Acts as a transducer if a transformer is given in `functor`.
*
* Works on array-like/iterable/iterator
*/
export const reduce: Reduce = curryN(3, _reduce);