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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.

 
             		           
                               
                            
                                
               
Peek at the beginning of a given string to see if it matches a sequence.
             		                            
exports.starts = (string, literal, start) ->
  literal is string.substr start, literal.length
             		           
                               
                            
                                
               
Peek at the end of a given string to see if it matches a sequence.
             		                            
exports.ends = (string, literal, back) ->
  len = literal.length
  literal is string.substr string.length - len - (back or 0), len
             		           
                               
                            
                                
               
Trim out all falsy values from an array.
             		                            
exports.compact = (array) ->
  item for item in array when item
             		           
                               
                            
                                
               
Count the number of occurrences of a character in a string.
             		                            
exports.count = (string, letter) ->
  num = pos = 0
  num++ while pos = 1 + string.indexOf letter, pos
  num
             		           
                               
                            
                                
               
Merge objects, returning a fresh copy with attributes from both sides.
Used every time Base#compile is called, to allow properties in the
options hash to propagate down the tree without polluting other branches.
             		                            
exports.merge = (options, overrides) ->
  extend (extend {}, options), overrides
             		           
                               
                            
                                
               
Extend a source object with the properties of another object (shallow copy).
             		                            
extend = exports.extend = (object, properties) ->
  for all key, val of properties
    object[key] = val
  object
             		           
                               
                            
                                
               
Return a flattened version of an array.
Handy for getting a list of children from the nodes.
             		                            
exports.flatten = flatten = (array) ->
  flattened = []
  for element in array
    if element instanceof Array
      flattened = flattened.concat flatten element
    else
      flattened.push element
  flattened
             		           
                               
                            
                                
               
Delete a key from an object, returning the value. Useful when a node is
looking for a particular method in an options hash.
             		                            
exports.del = (obj, key) ->
  val =  obj[key]
  delete obj[key]
  val
             		           
                               
                            
                                
               
Gets the last item of an array(-like) object.
             		                            
exports.last = (array, back) -> array[array.length - (back or 0) - 1]