Module: ANTLR3::AST::Tree

Included in:
BaseTree
Defined in:
lib/antlr3/tree.rb

Overview

ANTLR Abstract Syntax Trees

As ANTLR is concerned, an Abstract Syntax Tree (AST) node is an object that wraps a token, a list of child trees, and some information about the collective source text embodied within the tree and its children.

The Tree module, like the Token and Stream modules, emulates an abstract base class for AST classes; it specifies the attributes that are expected of basic tree nodes as well as the methods trees need to implement.

Terminology

While much of this terminology is probably familiar to most developers, the following brief glossary is intended to clarify terminology used in code throughout the AST library:

payload

either a token value contained within a node or nil

flat list (nil tree)

a tree node without a token payload, but with more than one children – functions like an array of tree nodes

root

a top-level tree node, i.e. a node that does not have a parent

leaf

a node that does not have any children

siblings

all other nodes sharing the same parent as some node

ancestors

the list of successive parents from a tree node to the root node

error node

a special node used to represent an erroneous series of tokens from an input stream

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#child_index ⇒ Object

Returns the value of attribute child_index.



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# File 'lib/antlr3/tree.rb', line 226

def child_index
  @child_index
end

#column ⇒ Object (readonly)

Returns the value of attribute column.



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# File 'lib/antlr3/tree.rb', line 230

def column
  @column
end

#line ⇒ Object (readonly)

Returns the value of attribute line.



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# File 'lib/antlr3/tree.rb', line 229

def line
  @line
end

#start_index ⇒ Object

attr_accessor :parent



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# File 'lib/antlr3/tree.rb', line 224

def start_index
  @start_index
end

#stop_index ⇒ Object

Returns the value of attribute stop_index.



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# File 'lib/antlr3/tree.rb', line 225

def stop_index
  @stop_index
end

#text ⇒ Object (readonly)

Returns the value of attribute text.



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# File 'lib/antlr3/tree.rb', line 228

def text
  @text
end

#token ⇒ Object (readonly)

attr_reader :children



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# File 'lib/antlr3/tree.rb', line 232

def token
  @token
end

#type ⇒ Object (readonly)

Returns the value of attribute type.



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# File 'lib/antlr3/tree.rb', line 227

def type
  @type
end

Instance Method Details

#ancestors ⇒ Object 



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# File 'lib/antlr3/tree.rb', line 277

def ancestors
  each_ancestor.to_a
end

#depth ⇒ Object 



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# File 'lib/antlr3/tree.rb', line 258

def depth
  root? ? 0 : parent.depth + 1
end

#each_ancestor ⇒ Object 



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# File 'lib/antlr3/tree.rb', line 267

def each_ancestor
  block_given? or return( enum_for( :each_ancestor ) )
  cursor = self
  until cursor.root?
    yield( parent_node = cursor.parent )
    cursor = parent_node
  end
  return( self )
end

#has_child?(node) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/antlr3/tree.rb', line 254

def has_child?( node )
  children and children.include?( node )
end

#leaf? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/antlr3/tree.rb', line 250

def leaf?
  children.nil? or children.empty?
end

#root ⇒ Object 



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# File 'lib/antlr3/tree.rb', line 240

def root
  cursor = self
  until cursor.root?
    yield( parent_node = cursor.parent )
    cursor = parent_node
  end
  return( cursor )
end

#root? ⇒ Boolean Also known as: detached?

Returns:

  • (Boolean) 


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# File 'lib/antlr3/tree.rb', line 235

def root?
  parent.nil?
end

#siblings ⇒ Object 



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# File 'lib/antlr3/tree.rb', line 262

def siblings
  root? and return []
  parent.children.reject { | c | c.equal?( self ) }
end

#walk ⇒ Object 



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# File 'lib/antlr3/tree.rb', line 281

def walk
  block_given? or return( enum_for( :walk ) )
  stack = []
  cursor = self
  while true
    begin
      yield( cursor )
      stack.push( cursor.children.dup ) unless cursor.empty?
    rescue StopIteration
      # skips adding children to prune the node
    ensure
      break if stack.empty?
      cursor = stack.last.shift
      stack.pop if stack.last.empty?
    end
  end
  return self
end