Module: Locomotive::AstHelpers::AstNode

Included in:
RelationalAlgebra::RelAlgAstNode
Defined in:
lib/locomotive/tree_helpers/ast.rb

Overview

Implements the composite behaviour, thus a node with two children.

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#kind ⇒ Object

Returns the value of attribute kind.



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# File 'lib/locomotive/tree_helpers/ast.rb', line 17

def kind
  @kind
end

#left_child ⇒ Object

Returns the value of attribute left_child.



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# File 'lib/locomotive/tree_helpers/ast.rb', line 21

def left_child
  @left_child
end

#owner ⇒ Object

Returns the value of attribute owner.



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# File 'lib/locomotive/tree_helpers/ast.rb', line 17

def owner
  @owner
end

#right_child ⇒ Object

Returns the value of attribute right_child.



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# File 'lib/locomotive/tree_helpers/ast.rb', line 21

def right_child
  @right_child
end

#value ⇒ Object

Returns the value of attribute value.



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# File 'lib/locomotive/tree_helpers/ast.rb', line 17

def value
  @value
end

Instance Method Details

#has_left_child? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/locomotive/tree_helpers/ast.rb', line 66

def has_left_child?
  self.left_child != nil
end

#has_right_child? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/locomotive/tree_helpers/ast.rb', line 70

def has_right_child?
  self.right_child != nil
end

#initialize(kind, value = nil, left = nil, right = nil) ⇒ Object

Initialize the node with values.</b> An Astract Syntax Tree-Node has a

1. kind
2. value
3. a left child
4. a right child
5. some node specific annotations

The values 2. - 5. can be omitted because there can be some nodes with a kind only (e.g. separators). A node with neither left- nor right-child is a leaf-node.



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# File 'lib/locomotive/tree_helpers/ast.rb', line 39

def initialize(kind,
               value = nil,
               left = nil,
               right = nil)
  self.owner = nil
  self.kind, self.value = kind, value
  self.left_child  = left  if left  != nil
  self.right_child = right if right != nil
  self.traverse_strategy = DEFAULT_TRAVERSE_STRATEGY
end

#is_leaf? ⇒ Boolean

checks whether the node is a leaf or not

Returns:

  • (Boolean) 


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# File 'lib/locomotive/tree_helpers/ast.rb', line 76

def is_leaf?
  self.left_child == nil and
  self.right_child == nil
end

#traverse(strategy = nil, &block) ⇒ Object

Traverses the ast with a given strategy. If nothing given simple prefix-traversal is used



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# File 'lib/locomotive/tree_helpers/ast.rb', line 90

def traverse(strategy=nil, &block)
  @strategy ||= strategy || DEFAULT_TRAVERSE_STRATEGY
  @strategy.traverse(self, &block)
end

#traverse_strategy=(strategy) ⇒ Object 



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# File 'lib/locomotive/tree_helpers/ast.rb', line 81

def traverse_strategy=(strategy)
  @strategy = strategy
  self.left_child.traverse_strategy = strategy if self.has_left_child?
  self.right_child.traverse_strategy = strategy if self.has_right_child?
end