vendored parslet, deemed stable enough and better without dependency

lib/parslet/atoms/dsl.rb

@@ -0,0 +1,109 @@
+
+# A mixin module that defines operations that can be called on any subclass
+# of Parslet::Atoms::Base. These operations make parslets atoms chainable and 
+# allow combination of parslet atoms to form bigger parsers.
+#
+# Example: 
+#
+#   str('foo') >> str('bar')
+#   str('f').repeat
+#   any.absent?               # also called The Epsilon
+#
+module Parslet::Atoms::DSL
+  # Construct a new atom that repeats the current atom min times at least and
+  # at most max times. max can be nil to indicate that no maximum is present. 
+  #
+  # Example: 
+  #   # match any number of 'a's
+  #   str('a').repeat     
+  #
+  #   # match between 1 and 3 'a's
+  #   str('a').repeat(1,3)
+  #
+  def repeat(min=0, max=nil)
+    Parslet::Atoms::Repetition.new(self, min, max)
+  end
+  
+  # Returns a new parslet atom that is only maybe present in the input. This
+  # is synonymous to calling #repeat(0,1). Generated tree value will be 
+  # either nil (if atom is not present in the input) or the matched subtree. 
+  #
+  # Example: 
+  #   str('foo').maybe
+  #
+  def maybe
+    Parslet::Atoms::Repetition.new(self, 0, 1, :maybe)
+  end
+
+  # Chains two parslet atoms together as a sequence. 
+  #
+  # Example: 
+  #   str('a') >> str('b')
+  #
+  def >>(parslet)
+    Parslet::Atoms::Sequence.new(self, parslet)
+  end
+
+  # Chains two parslet atoms together to express alternation. A match will
+  # always be attempted with the parslet on the left side first. If it doesn't
+  # match, the right side will be tried. 
+  #
+  # Example:
+  #   # matches either 'a' OR 'b'
+  #   str('a') | str('b')
+  #
+  def |(parslet)
+    Parslet::Atoms::Alternative.new(self, parslet)
+  end
+  
+  # Tests for absence of a parslet atom in the input stream without consuming
+  # it. 
+  # 
+  # Example: 
+  #   # Only proceed the parse if 'a' is absent.
+  #   str('a').absent?
+  #
+  def absent?
+    Parslet::Atoms::Lookahead.new(self, false)
+  end
+
+  # Tests for presence of a parslet atom in the input stream without consuming
+  # it. 
+  # 
+  # Example: 
+  #   # Only proceed the parse if 'a' is present.
+  #   str('a').present?
+  #
+  def present?
+    Parslet::Atoms::Lookahead.new(self, true)
+  end
+  
+  # Alias for present? that will disappear in 2.0 (deprecated)
+  #
+  alias prsnt? present?
+
+  # Alias for absent? that will disappear in 2.0 (deprecated)
+  #
+  alias absnt? absent?
+
+  # Marks a parslet atom as important for the tree output. This must be used 
+  # to achieve meaningful output from the #parse method. 
+  #
+  # Example:
+  #   str('a').as(:b) # will produce {:b => 'a'}
+  #
+  def as(name)
+    Parslet::Atoms::Named.new(self, name)
+  end
+
+  # Captures a part of the input and stores it under the name given. This 
+  # is very useful to create self-referential parses. A capture stores
+  # the result of its parse (may be complex) on a successful parse action.
+  # 
+  # Example: 
+  #   str('a').capture(:b)  # will store captures[:b] == 'a'
+  # 
+  def capture(name)
+    Parslet::Atoms::Capture.new(self, name)
+  end
+end