Is it possible to get an "inverse" function of a Boolean function in javascript?

Question

I was looking to write an "all-or-nothing" function over an array. One approach is, of course, to leverage Array.prototype.every and do something like

function allOrNothing(arr, f, fInv) {
  return arr.every(f) || arr.every(fInv);
}

where f and fInv are indicator functions, and fInv is an "inverse" function of f. For example, if f = (x) => x != null, then fInv = (x) => x == null.

This leads me to think: is it possible to get the function fInv from f?

Not sure what you're asking. Are you just looking for ! (logical 'not')? As in fInv = x => !f(x) ? — Mark Reed
– Mark Reed, Commented Dec 3, 2021 at 20:05
In your trivial example, fInv is effectively "not f". For arbitrary functions, it depends on what behavior you expect, I suppose. Might work OK for pure functions that simply return boolean. — jarmod
– jarmod, Commented Dec 3, 2021 at 20:06

VLAZ · Accepted Answer · 2021-12-03 20:11:51Z

5

This function, given a function f as an input, returns its boolean inverse:

let invert = (f) => (x) => !f(x)

e.g.

let invert = (f) => (x) => !f(x)

let eq_five = (x) => x == 5
let neq_five = invert(eq_five)

console.log(eq_five(5)) // true
console.log(neq_five(5)) // false

edited Dec 3, 2021 at 20:11

VLAZ

29.6k9 gold badges65 silver badges88 bronze badges

answered Dec 3, 2021 at 20:09

Mikail Khan

1296 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Is it possible to get an "inverse" function of a Boolean function in javascript?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related