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helpers.coffee

#

This file contains the common helper functions that we'd like to share among the Lexer, Rewriter, and the Nodes. Merge objects, flatten arrays, count characters, that sort of thing.

 
             		           
                               
                            
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Set up exported variables for both Node.js and the browser.
             		                            
this.exports = this unless process?
helpers = exports.helpers = {}
             		           
                               
                            
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Cross-browser indexOf, so that IE can join the party.
             		                            
helpers.indexOf = indexOf = (array, item, from) ->
  return array.indexOf item, from if array.indexOf
  for other, index in array
    if other is item and (not from or (from <= index))
      return index
  -1
             		           
                               
                            
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Does a list include a value?
             		                            
helpers.include = include = (list, value) ->
  indexOf(list, value) >= 0
             		           
                               
                            
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Peek at the beginning of a given string to see if it matches a sequence.
             		                            
helpers.starts = starts = (string, literal, start) ->
  string.substring(start, (start or 0) + literal.length) is literal
             		           
                               
                            
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Peek at the end of a given string to see if it matches a sequence.
             		                            
helpers.ends = ends = (string, literal, back) ->
  start = string.length - literal.length - (back ? 0)
  string.substring(start, start + literal.length) is literal
             		           
                               
                            
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Trim out all falsy values from an array.
             		                            
helpers.compact = compact = (array) -> item for item in array when item
             		           
                               
                            
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Count the number of occurences of a character in a string.
             		                            
helpers.count = count = (string, letter) ->
  num = 0
  pos = indexOf string, letter
  while pos isnt -1
    num += 1
    pos = indexOf string, letter, pos + 1
  num
             		           
                               
                            
                 #               
               
Merge objects, returning a fresh copy with attributes from both sides.
Used every time BaseNode#compile is called, to allow properties in the
options hash to propagate down the tree without polluting other branches.
             		                            
helpers.merge = merge = (options, overrides) ->
  fresh = {}
  (fresh[key] = val) for all key, val of options
  (fresh[key] = val) for all key, val of overrides if overrides
  fresh
             		           
                               
                            
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Extend a source object with the properties of another object (shallow copy).
We use this to simulate Node's deprecated process.mixin
             		                            
helpers.extend = extend = (object, properties) ->
  (object[key] = val) for all key, val of properties
             		           
                               
                            
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Return a completely flattened version of an array. Handy for getting a
list of children from the nodes.
             		                            
helpers.flatten = flatten = (array) ->
  memo = []
  for item in array
    if item instanceof Array then memo = memo.concat(item) else memo.push(item)
  memo
             		           
                               
                            
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Delete a key from an object, returning the value. Useful when a node is
looking for a particular method in an options hash.
             		                            
helpers.del = del = (obj, key) ->
  val = obj[key]
  delete obj[key]
  val