Class: LogicTools::Implicant

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



55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 55

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.



36
37
38
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 36

def bits
  @bits
end

#count ⇒ Object (readonly)

The number of 1 of the implicant.



38
39
40
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 38

def count
  @count
end

#covers ⇒ Object

The bit values covered by the implicant.



40
41
42
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 40

def covers
  @covers
end

#mask ⇒ Object (readonly)

The positions of the X in the implicant.



34
35
36
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 34

def mask
  @mask
end

#prime ⇒ Object

Tell if the implicant is prime or not.



42
43
44
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 42

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



46
47
48
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 46

def var
  @var
end

Instance Method Details

#<=>(implicant) ⇒ Object

:nodoc:



102
103
104
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 102

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

#==(implicant) ⇒ Object

Compares with implicant



99
100
101
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 99

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

#[](i) ⇒ Object

Gets the value of bit i.



112
113
114
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 112

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

#[]=(i, b) ⇒ Object

Sets the value of bit i to b.



117
118
119
120
121
122
123
124
125
126
127
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 117

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.



107
108
109
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 107

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

#each(&blk) ⇒ Object

Iterates over the bits of the implicant.

Returns an enumerator if no block given.



90
91
92
93
94
95
96
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 90

def each(&blk)
    # No block given? Returns an enumerator
    return to_enum(:each) unless block_given?
    
    # Block given? Applies it on each bit.
    @bits.each_char(&blk)
end

#inspect ⇒ Object

:nodoc:



78
79
80
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 78

def inspect #:nodoc:
    @bits.dup
end

#merge(implicant) ⇒ Object

Creates a new implicant merging current implicant with imp.



131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 131

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.



74
75
76
 
# File 'lib/logic_tools/logicsimplify_qm.rb', line 74

def to_s # :nodoc:
    @bits
end