Is it possible to define an infix function?

Question

Is it possible to define my own infix function/operator in CoffeeScript (or in pure JavaScript)? e.g. I want to call

a foo b

or

Answer 1

Javascript doesn't include an infix notation for functions or sections for partial application. But it ships with higher order functions, which allow us to do almost everything:

// applicator for infix notation
const $ = (x, f, y) => f(x) (y);

// for left section
const $_ = (x, f) => f(x);

// for right section
const _$ = (f, y) => x => f(x) (y);

// non-commutative operator function
const sub = x => y => x - y;


// application

console.log(
  $(2, sub, 3),   // -1
  $_(2, sub) (3), // -1
  _$(sub, 3) (2)  // -1
);

As you can see I prefer visual names $, $_ and _$ to textual ones in this case. This is the best you can get - at least with pure Javascript/ES2015.