82 lines
2.9 KiB
JavaScript
82 lines
2.9 KiB
JavaScript
//#region src/compat/function/curry.ts
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/**
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* Creates a function that accepts arguments of `func` and either invokes `func` returning its result, if at least `arity` number of arguments have been provided, or returns a function that accepts the remaining `func` arguments, and so on.
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* The arity of `func` may be specified if `func.length` is not sufficient.
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*
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* The `curry.placeholder` value, which defaults to a `symbol`, may be used as a placeholder for partially applied arguments.
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*
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* Note: This method doesn't set the `length` property of curried functions.
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*
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* @param {(...args: any[]) => any} func - The function to curry.
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* @param {number=func.length} arity - The arity of func.
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* @param {unknown} guard - Enables use as an iteratee for methods like `Array#map`.
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* @returns {((...args: any[]) => any) & { placeholder: typeof curry.placeholder }} - Returns the new curried function.
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*
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* @example
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* const abc = function(a, b, c) {
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* return Array.from(arguments);
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* };
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*
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* let curried = curry(abc);
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*
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* curried(1)(2)(3);
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* // => [1, 2, 3]
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*
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* curried(1, 2)(3);
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* // => [1, 2, 3]
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*
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* curried(1, 2, 3);
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* // => [1, 2, 3]
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*
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* // Curried with placeholders.
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* curried(1)(curry.placeholder, 3)(2);
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* // => [1, 2, 3]
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*
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* // Curried with arity.
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* curried = curry(abc, 2);
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*
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* curried(1)(2);
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* // => [1, 2]
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*/
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function curry(func, arity = func.length, guard) {
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arity = guard ? func.length : arity;
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arity = Number.parseInt(arity, 10);
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if (Number.isNaN(arity) || arity < 1) arity = 0;
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const wrapper = function(...partialArgs) {
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const holders = partialArgs.filter((item) => item === curry.placeholder);
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const length = partialArgs.length - holders.length;
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if (length < arity) return makeCurry(func, arity - length, partialArgs);
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if (this instanceof wrapper) return new func(...partialArgs);
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return func.apply(this, partialArgs);
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};
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wrapper.placeholder = curryPlaceholder;
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return wrapper;
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}
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function makeCurry(func, arity, partialArgs) {
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function wrapper(...providedArgs) {
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const holders = providedArgs.filter((item) => item === curry.placeholder);
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const length = providedArgs.length - holders.length;
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providedArgs = composeArgs(providedArgs, partialArgs);
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if (length < arity) return makeCurry(func, arity - length, providedArgs);
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if (this instanceof wrapper) return new func(...providedArgs);
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return func.apply(this, providedArgs);
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}
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wrapper.placeholder = curryPlaceholder;
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return wrapper;
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}
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function composeArgs(providedArgs, partialArgs) {
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const args = [];
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let startIndex = 0;
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for (let i = 0; i < partialArgs.length; i++) {
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const arg = partialArgs[i];
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if (arg === curry.placeholder && startIndex < providedArgs.length) args.push(providedArgs[startIndex++]);
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else args.push(arg);
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}
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for (let i = startIndex; i < providedArgs.length; i++) args.push(providedArgs[i]);
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return args;
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}
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const curryPlaceholder = Symbol("curry.placeholder");
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curry.placeholder = curryPlaceholder;
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//#endregion
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exports.curry = curry;
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