Class: LogicTools::NodeNot

Inherits:
NodeUnary show all
Defined in:
lib/logic_tools/logictree.rb

Overview

Represents a NOT node.

Instance Attribute Summary

Attributes inherited from NodeUnary

#child, #op

Instance Method Summary collapse

Methods inherited from NodeUnary

#==, #each, #get_variablesRecurse, #include?, #is_parent?, #size, #to_sym

Methods inherited from Node

#cover?, #distribute, #each, #each_line, #each_maxterm, #each_minterm, #eql?, #get_variables, #hash, #include?, #inspect, #is_parent?, #op, #reduce, #simplify, #size, #to_cover, #to_std_conjunctive, #to_std_disjunctive, #to_sym

Constructor Details

#initialize(child) ⇒ NodeNot

Creates a NOT node with a child.



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# File 'lib/logic_tools/logictree.rb', line 920

def initialize(child)
    super(:not,child)
end

Instance Method Details

#dup ⇒ Object

Duplicates the node.



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# File 'lib/logic_tools/logictree.rb', line 925

def dup # :nodoc:
    return NodeNot.new(@child.dup)
end

#eval ⇒ Object

Computes the value of the node.



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# File 'lib/logic_tools/logictree.rb', line 930

def eval # :nodoc:
    return !child.eval
end

#flatten ⇒ Object

Creates a new tree where the and, or or not operator of

the current node is flattened.

Default: simply duplicates the node.



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# File 'lib/logic_tools/logictree.rb', line 938

def flatten # :nodoc:
    nchild = @child.flatten
    if nchild.op == :not then
        return nchild.child
    else
        return NodeNot.new(nchild)
    end
end

#flatten_deep ⇒ Object

Creates a new tree where all the and, or and not operators

from the current node are flattened.

Default: simply duplicate.



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# File 'lib/logic_tools/logictree.rb', line 951

def flatten_deep # :nodoc:
    nchild = @child.flatten_deep
    if nchild.op == :not then
        return nchild.child
    else
        return NodeNot.new(child)
    end
end

#to_s ⇒ Object

Converts to a string.



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# File 'lib/logic_tools/logictree.rb', line 990

def to_s # :nodoc:
    return @str if @str
    # Is the child a binary node?
    if child.op == :or || child.op == :and then
        # Yes must put parenthesis
        @str = "~(" + child.to_s + ")"
    else
        # No
        @str = "~" + child.to_s
    end
    return @str
end

#to_sum_product(flattened = false) ⇒ Object

Creates a sum fo product from the tree rooted by current node.

Argument +flattened+ tells if the tree is already flattend



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# File 'lib/logic_tools/logictree.rb', line 963

def to_sum_product(flattened = false) # :nodoc:
    # return NodeNot.new(@child.to_sum_product(flatten))
    # Flatten deeply if required.
    nnode = flattened ? self : self.flatten_deep
    if (nnode.op != :not) then
        # Not a NOT any longer.
        return nnode.to_sum_product
    end
    # Still a NOT, so apply De Morgan's law.
    child = nnode.child
    if child.op == :or then
        # Can apply De Morgan's law for OR.
        return NodeAnd.new( *child.each.map do |n|
            NodeNot.new(n).to_sum_product
        end ).to_sum_product
    elsif child.op == :and then
        # Can apply De Morgan's law for AND.
        return NodeOr.new( *child.each.map do |n|
            NodeNot.new(n).to_sum_product
        end )
    else
        # Nothing to do more.
        return nnode
    end
end