jashkenas--coffeescript/examples/underscore.coffee

# Underscore.js
# (c) 2009 Jeremy Ashkenas, DocumentCloud Inc.
# Underscore is freely distributable under the terms of the MIT license.
# Portions of Underscore are inspired by or borrowed from Prototype.js,
# Oliver Steele's Functional, and John Resig's Micro-Templating.
# 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._

# 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

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

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

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

# Create quick reference variables for speed access to core prototypes.
slice:                Array.prototype.slice
unshift:              Array.prototype.unshift
toString:             Object.prototype.toString
hasOwnProperty:       Object.prototype.hasOwnProperty
propertyIsEnumerable: Object.prototype.propertyIsEnumerable

# Current version.
_.VERSION: '0.5.1'

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

# The cornerstone, an each implementation.
# Handles objects implementing forEach, arrays, and raw objects.
_.each: obj, iterator, context =>
  index: 0
  try
    return obj.forEach(iterator, context) if obj.forEach
    if _.isArray(obj) or _.isArguments(obj)
      return iterator.call(context, item, i, obj) for item, i in obj 
    iterator.call(context, obj[key], key, obj) for key in _.keys(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 (obj and _.isFunction(obj.map))
  results: []
  mapper: value, index, list => results.push(iterator.call(context, value, index, list))
  _.each(obj, mapper)
  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 (obj and _.isFunction(obj.reduce))
  reducer: value, index, list => memo: iterator.call(context, memo, value, index, list)
  _.each(obj, reducer)
  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 (obj and _.isFunction(obj.reduceRight))
  reversed: _.clone(_.toArray(obj)).reverse()
  reverser: value, index => memo: iterator.call(context, memo, value, index, obj)
  _.each(reversed, reverser)
  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.
_.select: obj, iterator, context =>
  if obj and _.isFunction(obj.filter) then return obj.filter(iterator, context)
  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.
_.all: obj, iterator, context =>
  iterator ||= _.identity
  return obj.every(iterator, context) if obj and _.isFunction(obj.every)
  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.
_.any: obj, iterator, context =>
  iterator ||= _.identity
  return obj.some(iterator, context) if obj and _.isFunction(obj.some)
  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 _.isArray(obj)
  found: false
  _.each(obj, (value =>
    _.breakLoop() if (found: value is target)))
  found

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

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

# Return the maximum item or (item-based computation).
_.max: obj, iterator, context =>
  return Math.max.apply(Math, obj) if !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 = function(obj, iterator, context) {
#     if (!iterator && _.isArray(obj)) return Math.min.apply(Math, obj);
#     var result = {computed : Infinity};
#     _.each(obj, function(value, index, list) {
#       var computed = iterator ? iterator.call(context, value, index, list) : value;
#       computed < result.computed && (result = {value : value, computed : computed});
#     });
#     return result.value;
#   };
#
#   # Sort the object's values by a criteria produced by an iterator.
#   _.sortBy = function(obj, iterator, context) {
#     return _.pluck(_.map(obj, function(value, index, list) {
#       return {
#         value : value,
#         criteria : iterator.call(context, value, index, list)
#       };
#     }).sort(function(left, right) {
#       var a = left.criteria, b = right.criteria;
#       return a < b ? -1 : a > b ? 1 : 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 = function(array, obj, iterator) {
#     iterator = iterator || _.identity;
#     var low = 0, high = array.length;
#     while (low < high) {
#       var mid = (low + high) >> 1;
#       iterator(array[mid]) < iterator(obj) ? low = mid + 1 : high = mid;
#     }
#     return low;
#   };
#
#   # Convert anything iterable into a real, live array.
#   _.toArray = function(iterable) {
#     if (!iterable)                return [];
#     if (iterable.toArray)         return iterable.toArray();
#     if (_.isArray(iterable))      return iterable;
#     if (_.isArguments(iterable))  return slice.call(iterable);
#     return _.map(iterable, function(val){ return val; });
#   };
#
#   # Return the number of elements in an object.
#   _.size = function(obj) {
#     return _.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 = function(array, n, guard) {
#     return n && !guard ? slice.call(array, 0, n) : 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 = function(array, index, guard) {
#     return slice.call(array, _.isUndefined(index) || guard ? 1 : index);
#   };
#
#   # Get the last element of an array.
#   _.last = function(array) {
#     return array[array.length - 1];
#   };
#
#   # Trim out all falsy values from an array.
#   _.compact = function(array) {
#     return _.select(array, function(value){ return !!value; });
#   };
#
#   # Return a completely flattened version of an array.
#   _.flatten = function(array) {
#     return _.reduce(array, [], function(memo, value) {
#       if (_.isArray(value)) return memo.concat(_.flatten(value));
#       memo.push(value);
#       return memo;
#     });
#   };
#
#   # Return a version of the array that does not contain the specified value(s).
#   _.without = function(array) {
#     var values = _.rest(arguments);
#     return _.select(array, function(value){ return !_.include(values, value); });
#   };
#
#   # 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 = function(array, isSorted) {
#     return _.reduce(array, [], function(memo, el, i) {
#       if (0 == i || (isSorted === true ? _.last(memo) != el : !_.include(memo, el))) memo.push(el);
#       return memo;
#     });
#   };
#
#   # Produce an array that contains every item shared between all the
#   # passed-in arrays.
#   _.intersect = function(array) {
#     var rest = _.rest(arguments);
#     return _.select(_.uniq(array), function(item) {
#       return _.all(rest, function(other) {
#         return _.indexOf(other, item) >= 0;
#       });
#     });
#   };
#
#   # Zip together multiple lists into a single array -- elements that share
#   # an index go together.
#   _.zip = function() {
#     var args = _.toArray(arguments);
#     var length = _.max(_.pluck(args, 'length'));
#     var results = new Array(length);
#     for (var i=0; i<length; i++) results[i] = _.pluck(args, String(i));
#     return 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 = function(array, item) {
#     if (array.indexOf) return array.indexOf(item);
#     for (var i=0, l=array.length; i<l; i++) if (array[i] === item) return i;
#     return -1;
#   };
#
#   # Provide JavaScript 1.6's lastIndexOf, delegating to the native function,
#   # if possible.
#   _.lastIndexOf = function(array, item) {
#     if (array.lastIndexOf) return array.lastIndexOf(item);
#     var i = array.length;
#     while (i--) if (array[i] === item) return i;
#     return -1;
#   };
#
#   # Generate an integer Array containing an arithmetic progression. A port of
#   # the native Python range() function. See:
#   # http://docs.python.org/library/functions.html#range
#   _.range = function(start, stop, step) {
#     var a     = _.toArray(arguments);
#     var solo  = a.length <= 1;
#     var start = solo ? 0 : a[0], stop = solo ? a[0] : a[1], step = a[2] || 1;
#     var len   = Math.ceil((stop - start) / step);
#     if (len <= 0) return [];
#     var range = new Array(len);
#     for (var i = start, idx = 0; true; i += step) {
#       if ((step > 0 ? i - stop : stop - i) >= 0) return range;
#       range[idx++] = i;
#     }
#   };

# ----------------------- 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(_.toArray(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 = function(obj) {
#     var funcs = _.rest(arguments);
#     if (funcs.length == 0) funcs = _.functions(obj);
#     _.each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
#     return obj;
#   };
#
#   # Delays a function for the given number of milliseconds, and then calls
#   # it with the arguments supplied.
#   _.delay = function(func, wait) {
#     var args = _.rest(arguments, 2);
#     return setTimeout(function(){ return 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(_.toArray(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: _.toArray(arguments)
  =>
    args: _.toArray(arguments)
    args: [funcs[i]].apply(this, args) for i in [(funcs.length - 1)..0]
    args[0]

#   /* ------------------------- Object Functions: ---------------------------- */
#
#   # Retrieve the names of an object's properties.
#   _.keys = function(obj) {
#     if(_.isArray(obj)) return _.range(0, obj.length);
#     var keys = [];
#     for (var key in obj) if (hasOwnProperty.call(obj, key)) keys.push(key);
#     return keys;
#   };
#
#   # Retrieve the values of an object's properties.
#   _.values = function(obj) {
#     return _.map(obj, _.identity);
#   };
#
#   # Return a sorted list of the function names available in Underscore.
#   _.functions = function(obj) {
#     return _.select(_.keys(obj), function(key){ return _.isFunction(obj[key]); }).sort();
#   };
#
#   # Extend a given object with all of the properties in a source object.
#   _.extend = function(destination, source) {
#     for (var property in source) destination[property] = source[property];
#     return destination;
#   };
#
#   # Create a (shallow-cloned) duplicate of an object.
#   _.clone = function(obj) {
#     if (_.isArray(obj)) return obj.slice(0);
#     return _.extend({}, 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.
  # for (var key in a) if (!_.isEqual(a[key], b[key])) return false;
  return true

# Is a given array or object empty?
_.isEmpty: obj => _.keys(obj).length is 0

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

# Is a given variable an arguments object?
_.isArguments: obj => obj and _.isNumber(obj.length) and !_.isArray(obj) and !propertyIsEnumerable.call(obj, 'length')

# 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 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'

# 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

#   # Define the isArray, isDate, isFunction, isNumber, isRegExp, and isString
#   # functions based on their toString identifiers.
#   var types = ['Array', 'Date', 'Function', 'Number', 'RegExp', 'String'];
#   for (var i=0, l=types.length; i<l; i++) {
#     (function() {
#       var identifier = '[object ' + types[i] + ']';
#       _['is' + types[i]] = function(obj) { return toString.call(obj) == identifier; };
#     })();
#   }

# -------------------------- 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

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

#   # Generate a unique integer id (unique within the entire client session).
#   # Useful for temporary DOM ids.
#   var idCounter = 0;
#   _.uniqueId = function(prefix) {
#     var id = idCounter++;
#     return prefix ? prefix + id : id;
#   };
#
#   # JavaScript templating a-la ERB, pilfered from John Resig's
#   # "Secrets of the JavaScript Ninja", page 83.
#   _.template = function(str, data) {
#     var fn = new Function('obj',
#       'var p=[],print=function(){p.push.apply(p,arguments);};' +
#       'with(obj){p.push(\'' +
#       str
#         .replace(/[\r\t\n]/g, " ")
#         .split("<%").join("\t")
#         .replace(/((^|%>)[^\t]*)'/g, "$1\r")
#         .replace(/\t=(.*?)%>/g, "',$1,'")
#         .split("\t").join("');")
#         .split("%>").join("p.push('")
#         .split("\r").join("\\'")
#     + "');}return p.join('');");
#     return data ? fn(data) : fn;
#   };

# ------------------------------- Aliases ----------------------------------

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

#   /*------------------------ Setup the OOP Wrapper: --------------------------*/
#
#   # Helper function to continue chaining intermediate results.
#   var result = function(obj, chain) {
#     return chain ? _(obj).chain() : obj;
#   };
#
#   # Add all of the Underscore functions to the wrapper object.
#   _.each(_.functions(_), function(name) {
#     var method = _[name];
#     wrapper.prototype[name] = function() {
#       unshift.call(arguments, this._wrapped);
#       return result(method.apply(_, arguments), this._chain);
#     };
#   });
#
#   # Add all mutator Array functions to the wrapper.
#   _.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
#     var method = Array.prototype[name];
#     wrapper.prototype[name] = function() {
#       method.apply(this._wrapped, arguments);
#       return result(this._wrapped, this._chain);
#     };
#   });
#
#   # Add all accessor Array functions to the wrapper.
#   _.each(['concat', 'join', 'slice'], function(name) {
#     var method = Array.prototype[name];
#     wrapper.prototype[name] = function() {
#       return result(method.apply(this._wrapped, arguments), this._chain);
#     };
#   });
#
#   # Start chaining a wrapped Underscore object.
#   wrapper.prototype.chain = function() {
#     this._chain = true;
#     return this;
#   };
#
#   # Extracts the result from a wrapped and chained object.
#   wrapper.prototype.value = function() {
#     return this._wrapped;
#   };
#
#