mrkd
12/3/2015 - 3:54 PM

js-good-parts-fun-with-functions.html

js-good-parts-fun-with-functions.html
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<html><body><pre><script>
"use strict";
function log(arg) {
    document.writeln(arg);
}

function identity(x) {
    return x;
}
log(identity(3));

function add(x, y) {
    return x + y;
}
function mul(x,y) {
    return x * y;
}
function sub(x,y) {
    return x - y;
}


log("add: " + add(2,2));
log("mul: " + mul(2,4));
log("sub: " + sub(2,2));


// Write a function that takes an argument and returns a
// function that returns that argument.
function identityf(argument) {
    return function () {
        return argument;
    }
}

var three = identityf(3);

log("identityf: " + three());

// Write a function that adds from two invocations.
function addf(first) {
    return function(second) {
        return first + second;
    }
}

log("addf: " + addf(3)(4));

// Write a function liftf that takes a binary function, and
// makes it callable with two invocations
function liftf(binary) {
    return function(first) {
        return function(second) {
            return binary(first,second);
        }
    }
}

var addf = liftf(add);
log("liftf: " + addf(3)(4));


// function curry
function curry(binary, first) {
    return function(second) {
        return binary(first, second);
    }
}

var add3 = curry(add, 3);
log("curry: " + add3(4));
log("curry(mul, 5)(6): " + curry(mul, 5)(6));





</script></pre></body></html>