Composition & Monads — Series 2

Preview — 3 of 10 questions

javascript

const compose = (...fns) => x => fns.reduceRight((acc, fn) => fn(acc), x);
const double = x => x * 2;
const inc = x => x + 1;
const f = compose(double, inc);
console.log(f(5));

A11

B12

D10

javascript

const curry = fn => (...args) =>
  args.length >= fn.length ? fn(...args) : (...more) => curry(fn)(...args, ...more);
const add3 = curry((a, b, c) => a + b + c);
console.log(add3(1)(2)(3), add3(1, 2)(3), add3(1, 2, 3));

A6 undefined 6

BNaN NaN 6

C6 6 6

D1 3 6

What's the key conceptual difference between currying and partial application?

APartial application only works with arrow functions; currying only works with regular function declarations

BThey are exactly the same technique, just named differently by different communities

CCurrying can only be applied to functions with exactly two parameters

DCurrying transforms a function into a chain of unary (single-argument) functions; partial application is the more general act of pre-filling any subset of arguments, which can still return a function that accepts several remaining arguments at once

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