Composition & Monads — Series 3

Preview — 3 of 10 questions

What is logged?

javascript

const pipe = (...fns) => (x) => fns.reduce((acc, f) => f(acc), x);

const trim = (s) => s.trim();
const words = (s) => s.split(/\s+/);
const count = (a) => a.length;

console.log(pipe(trim, words, count)('  hello brave new world  '));

D24

What is logged?

javascript

const _ = Symbol('_');

const partial = (fn, ...preset) => (...later) => {
  const args = preset.map((p) => (p === _ ? later.shift() : p));
  return fn(...args, ...later);
};

const greet = (greeting, name, punct) => `${greeting}, ${name}${punct}`;
const hi = partial(greet, 'Hi', _, '!');

console.log(hi('Ada'));

AHi, Ada!

BHi, !Ada

CHi, Symbol(_)!

DAda, Hi!

Which statement distinguishes them correctly?

AThey are two names for the same transformation.

BCurrying fixes some arguments and returns a function of the rest; partial application splits a function into a chain of single-argument functions.

CPartial application only works on pure functions; currying works on any function.

DCurrying transforms an n-argument function into a chain of single-argument functions; partial application fixes some arguments now and returns a function taking the remainder.

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