Class: Regex::PolyadicExpression

Inherits:
CompoundExpression show all
Defined in:
lib/regex/polyadic_expression.rb

Overview

Abstract class. An element that is part of a regular expression & that has its own child sub-expressions.

Instance Attribute Summary collapse

Attributes inherited from Expression

#begin_anchor, #end_anchor

Instance Method Summary collapse

Methods inherited from CompoundExpression

#atomic?

Methods inherited from Expression

#atomic?, #cardinality, #options, #to_str

Constructor Details

#initialize(theChildren) ⇒ PolyadicExpression

Constructor.



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# File 'lib/regex/polyadic_expression.rb', line 13

def initialize(theChildren)
  super()
  @children = theChildren
end

Instance Attribute Details

#children ⇒ Object (readonly)

The aggregation of child elements



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# File 'lib/regex/polyadic_expression.rb', line 10

def children
  @children
end

Instance Method Details

#<<(aChild) ⇒ Object

Append the given child to the list of children. TODO: assess whether to defer to a subclass NAryExpression



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# File 'lib/regex/polyadic_expression.rb', line 20

def <<(aChild)
  @children << aChild

  return self
end

#df_visitor ⇒ Object

Build a depth-first in-order children visitor. The visitor is implemented as an Enumerator.



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# File 'lib/regex/polyadic_expression.rb', line 28

def df_visitor()
  root = children # The visit will start from the children of this object

  visitor = Enumerator.new do |result| # result is a Yielder
    # Initialization part: will run once
    visit_stack = [root] # The LIFO queue of nodes to visit

    begin # Traversal part (as a loop)
      top = visit_stack.pop
      if top.kind_of?(Array)
        next if top.empty?
        currChild = top.pop
        visit_stack.push top
      else
        currChild = top
      end

      result << currChild # Return the visited child

      unless currChild.atomic?
        # in-order traversal implies LIFO queue
        children_to_enqueue = currChild.children.reverse
        visit_stack.push(children_to_enqueue)
      end
    end until visit_stack.empty?
  end
  
  return visitor
end