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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 string in a string.

exports.count = (string, substr) ->
  num = pos = 0
  return 1/0 unless substr.length
  num++ while pos = 1 + string.indexOf substr, pos

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 key, val of properties
    object[key] = val

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
      flattened.push element

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]

Gets the last item of an array(-like) object.

exports.last = (array, back) -> array[array.length - (back or 0) - 1]

Typical Array::some

exports.some = Array::some ? (fn) ->
  return true for e in this when fn e