Snippet

Variadic Curry Implementation with Argument Placeholder Resolution

Advanced functional programming in JavaScript utilizes currying with placeholder symbols to allow flexible, out-of-order partial argument application. By tracking positional placeholder symbols (Symbol) and dynamically filling missing arguments across invocation tiers, higher-order functions can defer execution until the required arity threshold is fulfilled.

snippet.js

javascript

const _ = Symbol('curry.placeholder');
 
function curry(fn, arity = fn.length) {
  return function curried(...args) {
    return function(...nextArgs) {
      const combined = args.map(arg => (arg === _ && nextArgs.length ? nextArgs.shift() : arg)).concat(nextArgs);
      const filledCount = combined.filter(arg => arg !== _).length;
      return filledCount >= arity ? fn(...combined) : curried(...combined);
    };
  };
}
 
const divide = (a, b, c) => (a / b) + c;
const curriedDivide = curry(divide)();
const divideTenBy = curriedDivide(10, _, 2);
console.log(divideTenBy(5));

nodejs

Breakdown

const _ = Symbol('curry.placeholder');

Creates a unique, non-colliding symbol token to serve as a positional argument placeholder.

const combined = args.map(...).concat(nextArgs);

Merges incoming arguments into placeholders from prior function invocations in order.

return filledCount >= arity ? fn(...combined) : curried(...combined);

Evaluates resolved non-placeholder argument count against required arity before execution.

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Variadic Curry Implementation with Argument Placeholder Resolution

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