exports.extend = function(obj) {
    ArrayExt.extend(obj)
}

var ArrayExt = exports.ArrayExt = {
    
    extend: function(obj) {
        Object.keys(this).forEach(function(k) {
            if (k === 'extend' || obj[k]) return
            var fn = this[k]
            obj[k] = function() {
                fn.apply(this, [this].concat([].slice.call(arguments)))
            }
        })
    }

// abbrev
// assoc

    // [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
    // rassoc

  , 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
    }
}