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dlwjiang/expanded-factorial.js

Last active August 5, 2018 23:50
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expanded y-combinator factorial
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expanded-factorial.js
// This writes out the same function twice.
// If you consider the top function `pseudoFactorial` and the bottom function as `copy`
// you can read it as `pseudoFactorial(copy)`
//
// As pseudoFactorial creates a function that creates a function,
// this creates the factorial function, ready to take in `n`
const factorial = (f => n => {
if (n < 2) return 1;
return n * f(f)(n-1);
})(f => n => {
if (n < 2) return 1;
return n * f(f)(n-1);
})
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