Confused about javascript function returning multiple functions with many fat arrow

Question

I have problem with my cs homework. I need to access the x value of the function, but my codes is returning me an empty function instead of with the values

I have googled all the currying and closures, but none of them are advanced enough to help me solve my problem

const pair = (x, y) => f => f(x, y);  // Do not edit this function
const head = p => //Answer here                

console.log(head(pair(1,2)))          // Do not edit this

my console keeps returning me functions instead when I try all the combinations

function(a,b){return a;}

adiga · Accepted Answer · 2019-08-31 09:19:14Z

1

You could change head function like this:

const pair = (x, y) => f => f(x, y); 
const head = f => f(a => a)

console.log(head(pair(1,2)))

edited Aug 31, 2019 at 9:19

answered Aug 31, 2019 at 8:52

adiga

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6 Comments

adiga Over a year ago

@Peter here, pair is executed before head. You can add console.log() to check it.

adiga Over a year ago

@Peter saw your edit to the question now. Updated head

adiga Over a year ago

@Peter I didn't get you. "pass in function as a params" where?

Peter Over a year ago

@ adiga I don't get the f(a=> a) part after looking at it for a super long time

adiga Over a year ago

a => a is an arrow function just like (x, y) => f. You can write it like (a, b) => a if it's too confusing

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Jack Bashford · Accepted Answer · 2019-08-31 08:54:04Z

1

my console keeps returning me this instead

function(a,b){return a;}

Let's make this easier to read. In ES5, your code looks like this:

var pair = function(x, y) {
  return function(f) {
    return f(x, y);
  }
};

var head = function(p) {
  return function(a, b) {
    return a;
  }
};

You need to pass the function returned from head to the function returned by pair(1, 2). So you need to swap which order you're calling the functions in:

console.log(pair(1, 2)(head()));

answered Aug 31, 2019 at 8:54

Jack Bashford

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1 Comment

Jack Bashford Over a year ago

Then swap the logic in each function.

adiga · Accepted Answer · 2019-09-02 17:08:31Z

0

Not sure if I understand your question correctly or not but I guess you are trying to do this

const pair = (x, y) => f => f(x, y); 
const head = (x, y) => x;

console.log((pair(1,2)(head)))

if not then this one from above is correct

const pair = (x, y) => f => f(x, y); 
const head = f => f(a => a);

console.log(head(pair(1,2)))

edited Sep 2, 2019 at 17:08

adiga

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answered Sep 2, 2019 at 16:02

Milind Agrawal

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2 Comments

adiga Over a year ago

What does this add? Both of these are already mentioned in the answers above

Milind Agrawal Over a year ago

First one is not same as above but second one yes. I was unable to comment their so mentioned that point here.

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