CODEWITHSUNDEEP
javascriptfunctional-programming
Lex27
Lex27

Reputation: 115

currying function instead of if condition in javascript

Tried to use curry function to write if condition (without "if" "true" and "false"). Have no idea how to do it right! Can anyone help and show me how to do it? 

const True = () => {};
const False = () => {};
const If = True => False => ifFunction(True)(False);

const ifFunction = If(True);
ifFunction('1')('2'); // 1

console.log(If(True)('1')('2'));  // 1
console.log(If(False)('1')('2')); // 2

It should return 1 or 2 depends on which function is getting pass to if condition. But this code does not work at all.

Upvotes: 6

Views: 915

Answers (3)

Aadit M Shah
Aadit M Shah

Reputation: 74204

Here's a way to implement True, False, and If without using any control flow statements like if...else or switch..case, control flow expressions like ?:, or higher-order functions.

const True  = 1;
const False = 0;

const If = Bool => Then => Else => [Else, Then][Bool];

console.log(If(True)('1')('2'));  // 1
console.log(If(False)('1')('2')); // 2

This is a defunctionalization of the Church encoding solution. Hence, it's more efficient.

Upvotes: 2

Nina Scholz
Nina Scholz

Reputation: 386578

By using Church_Booleans, you could use the following functions.

const
    TRUE = a => b => a,
    FALSE = a => b => b,
    IF = p => a => b => p(a)(b);

console.log(IF(TRUE)('1')('2'));  // 1
console.log(IF(FALSE)('1')('2')); // 2

Upvotes: 7

A1rPun
A1rPun

Reputation: 16847

What about this?

const True = () => true;
const False = () => false;
const If = exp => exp() ? a => b => a : a => b => b;

console.log(If(True)('1')('2'));  // 1
console.log(If(False)('1')('2')); // 2

Upvotes: 1

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