SICPのexcrise1.2をjavascriptで書いた

Ext1.2.js

// Exercise1.2
var calc = function(f){
    return function(){
        var tmp;
        for (var i = 0; i < arguments.length; i++){
            var num = arguments[i];
            if (typeof tmp === 'undefined'){
                tmp  =  num;
            }else{
                tmp  =  f(tmp,  num);
            }
        }
        return tmp;
    }};

var add = calc(function(x, y){ return x + y;});
var mul = calc(function(x, y){ return x * y;});
var div = calc(function(x, y){ return x / y;});
var sub = calc(function(x, y){ return x - y;});

console.log(add(5, 4, 3, 2, 1)); // 15
console.log(mul(5, 4, 3, 2, 1)); // 15
console.log(sub(5, 4, 3, 2, 1)); // -5
console.log(div(5, 4, 3, 2, 1)); // 0.20833..4
var ext1_2 = function(){
    return div(add(5, 4, sub(2
                            , sub(3
                                  , add(6, div(4, 5)))))
                    , calc(mul)(3
                                , sub(6, 2)
                                , sub(2, 7)));
};
console.log('EXT1.2 : ' + ext1_2());