Class: LogicTools::Implicant

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/logic_tools/logicsimplify.rb

Overview

Represents a logic implicant

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(base) ⇒ Implicant

Creates a new implicant from base.

Argument +base+ can be either another implicant or a bit string.



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# File 'lib/logic_tools/logicsimplify.rb', line 54

def initialize(base)
    if base.is_a?(Implicant)
        @covers = base.covers.dup
        @bits = base.bits.dup
        @mask = base.mask.dup
        @count = base.count
    else
        @bits = base.to_s
        unless @bits.match(/^[01]*$/)
            raise "Invalid bit string for an initial implicant: "+ @bits
        end
        @mask = " " * @bits.size
        @count = @bits.count("1")
        @covers = [ @bits ]
    end
    @prime = true # By default assumed prime
end

Instance Attribute Details

#bits ⇒ Object (readonly)

The bit vector of the implicant.



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# File 'lib/logic_tools/logicsimplify.rb', line 35

def bits
  @bits
end

#count ⇒ Object (readonly)

The number of 1 of the implicant.



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# File 'lib/logic_tools/logicsimplify.rb', line 37

def count
  @count
end

#covers ⇒ Object

The bit values covered by the implicant.



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# File 'lib/logic_tools/logicsimplify.rb', line 39

def covers
  @covers
end

#mask ⇒ Object (readonly)

The positions of the X in the implicant.



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# File 'lib/logic_tools/logicsimplify.rb', line 33

def mask
  @mask
end

#prime ⇒ Object

Tell if the implicant is prime or not.



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# File 'lib/logic_tools/logicsimplify.rb', line 41

def prime
  @prime
end

#var ⇒ Object

The variable associated with the implicant

Do not interfer at all with the class, so
public and fully accessible



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# File 'lib/logic_tools/logicsimplify.rb', line 45

def var
  @var
end

Instance Method Details

#<=>(implicant) ⇒ Object

:nodoc:



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# File 'lib/logic_tools/logicsimplify.rb', line 95

def <=>(implicant) #:nodoc:
    @bits <=> implicant.to_s
end

#==(implicant) ⇒ Object

Compares with implicant



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# File 'lib/logic_tools/logicsimplify.rb', line 92

def ==(implicant) # :nodoc:
    @bits == implicant.to_s
end

#[](i) ⇒ Object

Gets the value of bit i.



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# File 'lib/logic_tools/logicsimplify.rb', line 105

def [](i)
    @bits[i]
end

#[]=(i, b) ⇒ Object

Sets the value of bit i to b.



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# File 'lib/logic_tools/logicsimplify.rb', line 110

def []=(i,b)
    raise "Invalid bit value: #{b}" unless ["0","1","x"].include?(b)
    return if @bits[i] == b # Already set
    # Update count and mask
    @count -= 1 if @bits[i] == "1"    # One 1 less
    @count += 1 if b == "1"           # One 1 more
    @mask[i] = " " if @bits[i] == "x" # One x less
    @mask[i] = "x" if b == "x"        # One x more
    # Update the bit string
    @bits[i] = b 
end

#dup ⇒ Object

duplicates the implicant.



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# File 'lib/logic_tools/logicsimplify.rb', line 100

def dup # :nodoc:
    Implicant.new(self)
end

#each(&blk) ⇒ Object

Iterates over the bits of the implicant.



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# File 'lib/logic_tools/logicsimplify.rb', line 87

def each(&blk)
    @bits.each_char(&blk)
end

#inspect ⇒ Object

:nodoc:



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# File 'lib/logic_tools/logicsimplify.rb', line 77

def inspect #:nodoc:
    @bits.dup
end

#merge(implicant) ⇒ Object

Creates a new implicant merging current implicant with imp.



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# File 'lib/logic_tools/logicsimplify.rb', line 124

def merge(implicant)
    # Has implicant the same mask?
    return nil unless implicant.mask == @mask
    # First look for a 1-0 or 0-1 difference
    found = nil
    @bits.each_char.with_index do |b0,i|
        b1 = implicant.bits[i]
        # Bits are different
        if (b0 != b1) then
            # Stop if there where already a difference
            if (found)
                found = nil
                break
            end
            # A 0-1 or a 1-0 difference is found
            found = i
        end
    end
    # Can merge at bit found
    if found then
        # print "merge!\n"
        # Duplicate current implicant
        merged = self.dup
        # And update its x
        merged[found] = "x"
        # Finally update its covers
        merged.covers = @covers | implicant.covers
        return merged
    end
    # No merge
    return nil
end

#to_s ⇒ Object

Converts to a string



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# File 'lib/logic_tools/logicsimplify.rb', line 73

def to_s # :nodoc:
    @bits
end