jashkenas--coffeescript/examples/underscore.coffee

  # **Underscore.coffee
  # (c) 2010 Jeremy Ashkenas, DocumentCloud Inc.**
  # Underscore is freely distributable under the terms of the
  # [MIT license](http://en.wikipedia.org/wiki/MIT_License).
  # Portions of Underscore are inspired by or borrowed from
  # [Prototype.js](http://prototypejs.org/api), Oliver Steele's
  # [Functional](http://osteele.com), and John Resig's
  # [Micro-Templating](http://ejohn.com).
  # For all details and documentation:
  # http://documentcloud.github.com/underscore/


  # Baseline setup
  # --------------

  # Establish the root object, `window` in the browser, or `global` on the server.
  root: this


  # Save the previous value of the `_` variable.
  previousUnderscore: root._


  # Establish the object that gets thrown to break out of a loop iteration.
  # `StopIteration` is SOP on Mozilla.
  breaker: if typeof(StopIteration) is 'undefined' then '__break__' else StopIteration


  # Helper function to escape **RegExp** contents, because JS doesn't have one.
  escapeRegExp: (string) -> string.replace(/([.*+?^${}()|[\]\/\\])/g, '\\$1')


  # Save bytes in the minified (but not gzipped) version:
  ArrayProto:           Array.prototype
  ObjProto:             Object.prototype


  # Create quick reference variables for speed access to core prototypes.
  slice:                ArrayProto.slice
  unshift:              ArrayProto.unshift
  toString:             ObjProto.toString
  hasOwnProperty:       ObjProto.hasOwnProperty
  propertyIsEnumerable: ObjProto.propertyIsEnumerable


  # All **ECMA5** native implementations we hope to use are declared here.
  nativeForEach:        ArrayProto.forEach
  nativeMap:            ArrayProto.map
  nativeReduce:         ArrayProto.reduce
  nativeReduceRight:    ArrayProto.reduceRight
  nativeFilter:         ArrayProto.filter
  nativeEvery:          ArrayProto.every
  nativeSome:           ArrayProto.some
  nativeIndexOf:        ArrayProto.indexOf
  nativeLastIndexOf:    ArrayProto.lastIndexOf
  nativeIsArray:        Array.isArray
  nativeKeys:           Object.keys


  # Create a safe reference to the Underscore object for use below.
  _: (obj) -> new wrapper(obj)


  # Export the Underscore object for **CommonJS**.
  if typeof(exports) != 'undefined' then exports._: _


  # Export Underscore to global scope.
  root._: _


  # Current version.
  _.VERSION: '1.0.2'


  # Collection Functions
  # --------------------

  # The cornerstone, an **each** implementation.
  # Handles objects implementing **forEach**, arrays, and raw objects.
  _.each: (obj, iterator, context) ->
    try
      if nativeForEach and obj.forEach is nativeForEach
        obj.forEach iterator, context
      else if _.isNumber obj.length
        iterator.call(context, obj[i], i, obj) for i in [0...obj.length]
      else
        iterator.call(context, val, key, obj) for key, val of obj
    catch e
      throw e if e isnt breaker
    obj


  # Return the results of applying the iterator to each element. Use JavaScript
  # 1.6's version of **map**, if possible.
  _.map: (obj, iterator, context) ->
    return obj.map(iterator, context) if nativeMap and obj.map is nativeMap
    results: []
    _.each obj, (value, index, list) ->
      results.push iterator.call context, value, index, list
    results


  # **Reduce** builds up a single result from a list of values. Also known as
  # **inject**, or **foldl**. Uses JavaScript 1.8's version of **reduce**, if possible.
  _.reduce: (obj, memo, iterator, context) ->
    return obj.reduce(_.bind(iterator, context), memo) if nativeReduce and obj.reduce is nativeReduce
    _.each obj, (value, index, list) ->
      memo: iterator.call context, memo, value, index, list
    memo


  # The right-associative version of **reduce**, also known as **foldr**. Uses
  # JavaScript 1.8's version of **reduceRight**, if available.
  _.reduceRight: (obj, memo, iterator, context) ->
    return obj.reduceRight(_.bind(iterator, context), memo) if nativeReduceRight and obj.reduceRight is nativeReduceRight
    _.each _.clone(_.toArray(obj)).reverse(), (value, index) ->
      memo: iterator.call context, memo, value, index, obj
    memo


  # Return the first value which passes a truth test.
  _.detect: (obj, iterator, context) ->
    result: null
    _.each obj, (value, index, list) ->
      if iterator.call context, value, index, list
        result: value
        _.breakLoop()
    result


  # Return all the elements that pass a truth test. Use JavaScript 1.6's
  # **filter**, if it exists.
  _.filter: (obj, iterator, context) ->
    return obj.filter iterator, context if nativeFilter and obj.filter is nativeFilter
    results: []
    _.each obj, (value, index, list) ->
      results.push value if iterator.call context, value, index, list
    results


  # Return all the elements for which a truth test fails.
  _.reject: (obj, iterator, context) ->
    results: []
    _.each obj, (value, index, list) ->
      results.push value if not iterator.call context, value, index, list
    results


  # Determine whether all of the elements match a truth test. Delegate to
  # JavaScript 1.6's **every**, if it is present.
  _.every: (obj, iterator, context) ->
    iterator ||= _.identity
    return obj.every iterator, context if nativeEvery and obj.every is nativeEvery
    result: true
    _.each obj, (value, index, list) ->
      _.breakLoop() unless (result: result and iterator.call(context, value, index, list))
    result


  # Determine if at least one element in the object matches a truth test. Use
  # JavaScript 1.6's **some**, if it exists.
  _.some: (obj, iterator, context) ->
    iterator ||= _.identity
    return obj.some iterator, context if nativeSome and obj.some is nativeSome
    result: false
    _.each obj, (value, index, list) ->
      _.breakLoop() if (result: iterator.call(context, value, index, list))
    result


  # Determine if a given value is included in the array or object,
  # based on `===`.
  _.include: (obj, target) ->
    return _.indexOf(obj, target) isnt -1 if nativeIndexOf and obj.indexOf is nativeIndexOf
    for key, val of obj
      return true if val is target
    false


  # Invoke a method with arguments on every item in a collection.
  _.invoke: (obj, method) ->
    args: _.rest arguments, 2
    (if method then val[method] else val).apply(val, args) for val in obj


  # Convenience version of a common use case of **map**: fetching a property.
  _.pluck: (obj, key) ->
    _.map(obj, (val) -> val[key])


  # Return the maximum item or (item-based computation).
  _.max: (obj, iterator, context) ->
    return Math.max.apply(Math, obj) if not iterator and _.isArray(obj)
    result: {computed: -Infinity}
    _.each obj, (value, index, list) ->
      computed: if iterator then iterator.call(context, value, index, list) else value
      computed >= result.computed and (result: {value: value, computed: computed})
    result.value


  # Return the minimum element (or element-based computation).
  _.min: (obj, iterator, context) ->
    return Math.min.apply(Math, obj) if not iterator and _.isArray(obj)
    result: {computed: Infinity}
    _.each obj, (value, index, list) ->
      computed: if iterator then iterator.call(context, value, index, list) else value
      computed < result.computed and (result: {value: value, computed: computed})
    result.value


  # Sort the object's values by a criterion produced by an iterator.
  _.sortBy: (obj, iterator, context) ->
    _.pluck(((_.map obj, (value, index, list) ->
      {value: value, criteria: iterator.call(context, value, index, list)}
    ).sort((left, right) ->
      a: left.criteria; b: right.criteria
      if a < b then -1 else if a > b then 1 else 0
    )), 'value')


  # Use a comparator function to figure out at what index an object should
  # be inserted so as to maintain order. Uses binary search.
  _.sortedIndex: (array, obj, iterator) ->
    iterator ||= _.identity
    low:  0
    high: array.length
    while low < high
      mid: (low + high) >> 1
      if iterator(array[mid]) < iterator(obj) then low: mid + 1 else high: mid
    low


  # Convert anything iterable into a real, live array.
  _.toArray: (iterable) ->
    return []                   if (!iterable)
    return iterable.toArray()   if (iterable.toArray)
    return iterable             if (_.isArray(iterable))
    return slice.call(iterable) if (_.isArguments(iterable))
    _.values(iterable)


  # Return the number of elements in an object.
  _.size: (obj) -> _.toArray(obj).length


  # Array Functions
  # ---------------

  # Get the first element of an array. Passing `n` will return the first N
  # values in the array. Aliased as **head**. The `guard` check allows it to work
  # with **map**.
  _.first: (array, n, guard) ->
    if n and not guard then slice.call(array, 0, n) else array[0]


  # Returns everything but the first entry of the array. Aliased as **tail**.
  # Especially useful on the arguments object. Passing an `index` will return
  # the rest of the values in the array from that index onward. The `guard`
  # check allows it to work with **map**.
  _.rest: (array, index, guard) ->
    slice.call(array, if _.isUndefined(index) or guard then 1 else index)


  # Get the last element of an array.
  _.last: (array) -> array[array.length - 1]


  # Trim out all falsy values from an array.
  _.compact: (array) -> item for item in array when item


  # Return a completely flattened version of an array.
  _.flatten: (array) ->
    _.reduce array, [], (memo, value) ->
      return memo.concat(_.flatten(value)) if _.isArray value
      memo.push value
      memo


  # Return a version of the array that does not contain the specified value(s).
  _.without: (array) ->
    values: _.rest arguments
    val for val in _.toArray(array) when not _.include values, val


  # Produce a duplicate-free version of the array. If the array has already
  # been sorted, you have the option of using a faster algorithm.
  _.uniq: (array, isSorted) ->
    memo: []
    for el, i in _.toArray array
      memo.push el if i is 0 || (if isSorted is true then _.last(memo) isnt el else not _.include(memo, el))
    memo


  # Produce an array that contains every item shared between all the
  # passed-in arrays.
  _.intersect: (array) ->
    rest: _.rest arguments
    _.select _.uniq(array), (item) ->
      _.all rest, (other) ->
        _.indexOf(other, item) >= 0


  # Zip together multiple lists into a single array -- elements that share
  # an index go together.
  _.zip: ->
    length:  _.max _.pluck arguments, 'length'
    results: new Array length
    for i in [0...length]
      results[i]: _.pluck arguments, String i
    results


  # If the browser doesn't supply us with **indexOf** (I'm looking at you, MSIE),
  # we need this function. Return the position of the first occurence of an
  # item in an array, or -1 if the item is not included in the array.
  _.indexOf: (array, item) ->
    return array.indexOf item if nativeIndexOf and array.indexOf is nativeIndexOf
    i: 0; l: array.length
    while l - i
      if array[i] is item then return i else i++
    -1


  # Provide JavaScript 1.6's **lastIndexOf**, delegating to the native function,
  # if possible.
  _.lastIndexOf: (array, item) ->
    return array.lastIndexOf(item) if nativeLastIndexOf and array.lastIndexOf is nativeLastIndexOf
    i: array.length
    while i
      if array[i] is item then return i else i--
    -1


  # Generate an integer Array containing an arithmetic progression. A port of
  # [the native Python **range** function](http://docs.python.org/library/functions.html#range).
  _.range: (start, stop, step) ->
    a:        arguments
    solo:     a.length <= 1
    i: start: if solo then 0 else a[0]
    stop:     if solo then a[0] else a[1]
    step:     a[2] or 1
    len:      Math.ceil((stop - start) / step)
    return [] if len <= 0
    range:    new Array len
    idx:      0
    loop
      return range if (if step > 0 then i - stop else stop - i) >= 0
      range[idx]: i
      idx++
      i+= step


  # Function Functions
  # ------------------

  # Create a function bound to a given object (assigning `this`, and arguments,
  # optionally). Binding with arguments is also known as **curry**.
  _.bind: (func, obj) ->
    args: _.rest arguments, 2
    -> func.apply obj or root, args.concat arguments


  # Bind all of an object's methods to that object. Useful for ensuring that
  # all callbacks defined on an object belong to it.
  _.bindAll: (obj) ->
    funcs: if arguments.length > 1 then _.rest(arguments) else _.functions(obj)
    _.each funcs, (f) -> obj[f]: _.bind obj[f], obj
    obj


  # Delays a function for the given number of milliseconds, and then calls
  # it with the arguments supplied.
  _.delay: (func, wait) ->
    args: _.rest arguments, 2
    setTimeout((-> func.apply(func, args)), wait)


  # Defers a function, scheduling it to run after the current call stack has
  # cleared.
  _.defer: (func) ->
    _.delay.apply _, [func, 1].concat _.rest arguments


  # Returns the first function passed as an argument to the second,
  # allowing you to adjust arguments, run code before and after, and
  # conditionally execute the original function.
  _.wrap: (func, wrapper) ->
    -> wrapper.apply wrapper, [func].concat arguments


  # Returns a function that is the composition of a list of functions, each
  # consuming the return value of the function that follows.
  _.compose: ->
    funcs: arguments
    ->
      args: arguments
      for i in [(funcs.length - 1)..0]
        args: [funcs[i].apply(this, args)]
      args[0]


  # Object Functions
  # ----------------

  # Retrieve the names of an object's properties.
  _.keys: nativeKeys or (obj) ->
    return _.range 0, obj.length if _.isArray(obj)
    key for key, val of obj


  # Retrieve the values of an object's properties.
  _.values: (obj) ->
    _.map obj, _.identity


  # Return a sorted list of the function names available in Underscore.
  _.functions: (obj) ->
    _.filter(_.keys(obj), (key) -> _.isFunction(obj[key])).sort()


  # Extend a given object with all of the properties in a source object.
  _.extend: (obj) ->
    for source in _.rest(arguments)
      (obj[key]: val) for key, val of source
    obj


  # Create a (shallow-cloned) duplicate of an object.
  _.clone: (obj) ->
    return obj.slice 0 if _.isArray obj
    _.extend {}, obj


  # Invokes interceptor with the obj, and then returns obj.
  # The primary purpose of this method is to "tap into" a method chain, in order to perform operations on intermediate results within the chain.
  _.tap: (obj, interceptor) ->
    interceptor obj
    obj


  # Perform a deep comparison to check if two objects are equal.
  _.isEqual: (a, b) ->
    # Check object identity.
    return true if a is b
    # Different types?
    atype: typeof(a); btype: typeof(b)
    return false if atype isnt btype
    # Basic equality test (watch out for coercions).
    return true if `a == b`
    # One is falsy and the other truthy.
    return false if (!a and b) or (a and !b)
    # One of them implements an `isEqual()`?
    return a.isEqual(b) if a.isEqual
    # Check dates' integer values.
    return a.getTime() is b.getTime() if _.isDate(a) and _.isDate(b)
    # Both are NaN?
    return true if _.isNaN(a) and _.isNaN(b)
    # Compare regular expressions.
    if _.isRegExp(a) and _.isRegExp(b)
      return a.source     is b.source and
             a.global     is b.global and
             a.ignoreCase is b.ignoreCase and
             a.multiline  is b.multiline
    # If a is not an object by this point, we can't handle it.
    return false if atype isnt 'object'
    # Check for different array lengths before comparing contents.
    return false if a.length and (a.length isnt b.length)
    # Nothing else worked, deep compare the contents.
    aKeys: _.keys(a); bKeys: _.keys(b)
    # Different object sizes?
    return false if aKeys.length isnt bKeys.length
    # Recursive comparison of contents.
    (return false) for key, val of a when !(key in b) or !_.isEqual(val, b[key])
    true


  # Is a given array or object empty?
  _.isEmpty: (obj) ->
    return obj.length is 0 if _.isArray obj
    (return false) for key of obj when hasOwnProperty.call(obj, key)
    true


  # Is a given value a DOM element?
  _.isElement:    (obj) -> obj and obj.nodeType is 1


  # Is a given value an array?
  _.isArray:      nativeIsArray or (obj) -> !!(obj and obj.concat and obj.unshift and not obj.callee)


  # Is a given variable an arguments object?
  _.isArguments:  (obj) -> obj and obj.callee


  # Is the given value a function?
  _.isFunction:   (obj) -> !!(obj and obj.constructor and obj.call and obj.apply)


  # Is the given value a string?
  _.isString:     (obj) -> !!(obj is '' or (obj and obj.charCodeAt and obj.substr))


  # Is a given value a number?
  _.isNumber:     (obj) -> (obj is +obj) or toString.call(obj) is '[object Number]'


  # Is a given value a boolean?
  _.isBoolean:    (obj) -> obj is true or obj is false


  # Is a given value a Date?
  _.isDate:       (obj) -> !!(obj and obj.getTimezoneOffset and obj.setUTCFullYear)


  # Is the given value a regular expression?
  _.isRegExp:     (obj) -> !!(obj and obj.exec and (obj.ignoreCase or obj.ignoreCase is false))


  # Is the given value NaN -- this one is interesting. `NaN != NaN`, and
  # `isNaN(undefined) == true`, so we make sure it's a number first.
  _.isNaN:        (obj) -> _.isNumber(obj) and window.isNaN(obj)


  # Is a given value equal to null?
  _.isNull:       (obj) -> obj is null


  # Is a given variable undefined?
  _.isUndefined:  (obj) -> typeof obj is 'undefined'


  # Utility Functions
  # -----------------

  # Run Underscore.js in noConflict mode, returning the `_` variable to its
  # previous owner. Returns a reference to the Underscore object.
  _.noConflict: ->
    root._: previousUnderscore
    this


  # Keep the identity function around for default iterators.
  _.identity: (value) -> value


  # Run a function `n` times.
  _.times: (n, iterator, context) ->
    iterator.call(context, i) for i in [0...n]


  # Break out of the middle of an iteration.
  _.breakLoop: -> throw breaker


  # Add your own custom functions to the Underscore object, ensuring that
  # they're correctly added to the OOP wrapper as well.
  _.mixin: (obj) ->
    for name in _.functions(obj)
      addToWrapper name, _[name]: obj[name]


  # Generate a unique integer id (unique within the entire client session).
  # Useful for temporary DOM ids.
  idCounter: 0
  _.uniqueId: (prefix) ->
    (prefix or '') + idCounter++


  # By default, Underscore uses **ERB**-style template delimiters, change the
  # following template settings to use alternative delimiters.
  _.templateSettings: {
    start:        '<%'
    end:          '%>'
    interpolate:  /<%=(.+?)%>/g
  }


  # JavaScript templating a-la **ERB**, pilfered from John Resig's
  # *Secrets of the JavaScript Ninja*, page 83.
  # Single-quote fix from Rick Strahl.
  _.template: (str, data) ->
    c: _.templateSettings
    endMatch: new RegExp("'(?=[^"+c.end.substr(0, 1)+"]*"+escapeRegExp(c.end)+")","g")
    fn: new Function 'obj',
      'var p=[],print=function(){p.push.apply(p,arguments);};' +
      'with(obj){p.push(\'' +
      str.replace(/[\r\t\n]/g, " ")
         .replace(endMatch,"\t")
         .split("'").join("\\'")
         .split("\t").join("'")
         .replace(c.interpolate, "',$1,'")
         .split(c.start).join("');")
         .split(c.end).join("p.push('") +
         "');}return p.join('');"
    if data then fn(data) else fn


  # Aliases
  # -------

  _.forEach: _.each
  _.foldl:   _.inject:      _.reduce
  _.foldr:   _.reduceRight
  _.select:  _.filter
  _.all:     _.every
  _.any:     _.some
  _.head:    _.first
  _.tail:    _.rest
  _.methods: _.functions


  # Setup the OOP Wrapper
  # ---------------------

  # If Underscore is called as a function, it returns a wrapped object that
  # can be used OO-style. This wrapper holds altered versions of all the
  # underscore functions. Wrapped objects may be chained.
  wrapper: (obj) ->
    this._wrapped: obj
    this


  # Helper function to continue chaining intermediate results.
  result: (obj, chain) ->
    if chain then _(obj).chain() else obj


  # A method to easily add functions to the OOP wrapper.
  addToWrapper: (name, func) ->
    wrapper.prototype[name]: ->
      args: _.toArray arguments
      unshift.call args, this._wrapped
      result func.apply(_, args), this._chain


  # Add all of the Underscore functions to the wrapper object.
  _.mixin _


  # Add all mutator Array functions to the wrapper.
  _.each ['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], (name) ->
    method: Array.prototype[name]
    wrapper.prototype[name]: ->
      method.apply(this._wrapped, arguments)
      result(this._wrapped, this._chain)


  # Add all accessor Array functions to the wrapper.
  _.each ['concat', 'join', 'slice'], (name) ->
    method: Array.prototype[name]
    wrapper.prototype[name]: ->
      result(method.apply(this._wrapped, arguments), this._chain)


  # Start chaining a wrapped Underscore object.
  wrapper::chain: ->
    this._chain: true
    this


  # Extracts the result from a wrapped and chained object.
  wrapper::value: -> this._wrapped