gistfile1.txt

// Part 1.
// Implement a function prototype extension that caches function results for
// the same input arguments of a function with one parameter.
//
// For example:
// Make sin(1) have the result of Math.sin(1), but use a cached value
// for future calls.
//
// Part 2.
// Use this new function to refactor the code example.
// Some good test numbers: 524287, 9369319, 2147483647 (all primes)
//
// In other words, if you have this code:
//
//  Function.prototype.cached = function(){
//    ? (what goes here?)
//  }
//  
//  // For the isPrime function
//  
//  var cachedIsPrime = isPrime.cached();
//  isPrime(11); // --> true (cache miss, calls original isPrime(1) function, stores return value in cache)
//  isPrime(11); // --> true (cache hit, directly returns value)
//  
//  // ..but it short work on anything that takes just one (numeric) argument:
//  
//  var cachedSin = Math.sin.cached();
//  
//  cachedSin(1); // --> 0.8414709848078965 (cache miss, calls original Math.sin(1) function, stores return value in cache)
//  cachedSin(1); // --> 0.8414709848078965 (cache hit, directly returns value)


// NEEDS TO CHECK NO OF ARGUMENTS


Function.prototype.cached = function() {


    var self = this,
        cache = {};

    return function( arg ) {
    
        if ( arg in cache ) {

            console.log( 'cached' )
            return cache[arg];

        } else {

            return cache[arg] = self( arg );

        }

    }

}



function sin( num ) {

    return Math.sin( num);

}

cachedSin = Math.sin.cached();





function isPrime(num) {
    
    if (isPrime.cache[num] != null) return isPrime.cache[num];

    // everything but 1 can be prime
    var prime = num != 1;
    for (var i = 2; i < num; i++) {
        if (num % i == 0) {
            prime = false;
            break;
        }
    }

    isPrime.cache[num] = prime;
    return prime;
}

isPrime.cache = {};