exports.extendNative = function() {
    Object.keys(ArrayExt).forEach(function(k) {
        if (Array.prototype[k]) return; // don't overwrite existing members
        Array.prototype[k] = function() {
            var fn = ArrayExt[k]
              , args = [].slice.call(arguments)
              ;
            args.shift(this);
            fn.apply(ArrayExt, args);
        };
    });
};

var ArrayToString = [].toString();

var ArrayExt = exports.ArrayExt = {
    
// abbrev

    // [1,2,3,4,5].at(-1) => 5
    at: function(a, i) {
        if (i >= 0) return a[i];
        return a[a.length + i];
    }

    // TODO make this work for non-array objects
  , compact: function(a) {
        var b = []
          , i = a.length
          ;
        while (i--) {
            if (a[i] !== null && a[i] !== undefined) b[i] = a[i];
        }
        return b;
    }

  , first: function(a) { return a[0]; }
  
    // Based on underscore.js's flatten
  , flatten: function(a) {
        return a.reduce(function(initial, elem) {
            if (elem && elem.flatten) initial = initial.concat(elem.flatten());
            else initial.push(elem);
            return initial;
        });
    }

  , grep: function(a, regex) {
        return a.filter(function(v) { return regex.match(v); });
    }

  , last: function(a) { return a[a.length-1]; }

  , max: function(a) {
        return a.reduce(function(max, v) { return v > max ? v : max });
    }

  , min: function(a) {
        return a.reduce(function(min, v) { return v < min ? v : min });
    }

    // pack
    // partition

  , toString: function(a) {
        return '[' + ArrayToString.call(a) + ']';
    }

  , unique: function(a) {
        var b = []
          , i = 0
          , n = a.length
          ;
        for (; i < n; ++i) {
            if (b.indexOf(a[i]) === -1) b.push(a[i]);
        }
        return b;
    }
};