Class: TruthTable

Inherits:
Object
  • Object
show all
Defined in:
lib/truthtable.rb,
lib/truthtable/qm.rb

Defined Under Namespace

Modules: QM

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(&b) ⇒ TruthTable

Returns a new instance of TruthTable.



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# File 'lib/truthtable.rb', line 19

def initialize(&b)
  table = TruthTable.test(&b)
  @table = table
end

Class Method Details

.test(&b) ⇒ Object 



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# File 'lib/truthtable.rb', line 7

def self.test(&b)
  r = []
  o = TruthTableObject.new
  begin
    result = !!b.call(o)
    inputs = o.plan
    order = o.order
    r << [inputs, result, order]
  end while o.next_plan
  r
end

Instance Method Details

#all_names ⇒ Object 



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# File 'lib/truthtable.rb', line 92

def all_names
  return @all_names if defined? @all_names
  @all_names = {}
  @table.each {|inputs, output, order|
    order.each {|name|
      if !@all_names.has_key?(name)
        @all_names[name] = @all_names.size
      end
    }
  }
  @all_names
end

#cnf ⇒ Object

obtains a formula in conjunctive normal form.



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# File 'lib/truthtable.rb', line 138

def cnf
  r = []
  @table.each {|inputs, output|
    return output.to_s if inputs.empty?
    next if output
    term = []
    each_input(inputs) {|name, input|
      if input
        term << "!#{name}"
      else
        term << name
      end
    }
    if term.length == 1
      r << term.join('|')
    else
      r << "(#{term.join('|')})"
    end
  }
  return "true" if r.empty?
  r.join(' & ')
end

#dnf ⇒ Object

obtains a formula in disjunctive normal form.



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# File 'lib/truthtable.rb', line 118

def dnf
  r = []
  @table.each {|inputs, output|
    return output.to_s if inputs.empty?
    next if !output
    term = []
    each_input(inputs) {|name, input|
      if input
        term << name
      else
        term << "!#{name}"
      end
    }
    r << term.join('&')
  }
  return "false" if r.empty?
  r.join(' | ')
end

#each_input(inputs) ⇒ Object 



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# File 'lib/truthtable.rb', line 110

def each_input(inputs)
  sort_names(inputs.keys).each {|name|
    yield name, inputs[name]
  }
end

#formula ⇒ Object

obtains a minimal formula using Quine-McCluskey algorithm.



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# File 'lib/truthtable.rb', line 162

def formula
  input_names = all_names
  input_names_ary = sort_names(input_names.keys)
  tbl = {}
  @table.each {|inputs, output|
    return output.to_s if inputs.empty?
    inputs2 = [:x] * input_names.length
    inputs.each {|name, input|
      inputs2[input_names[name]] = input ? 1 : 0
    }
    tbl[inputs2] = output ? 1 : 0
  }
  qm = QM.qm(tbl)
  r = []
  qm.each {|term|
    t = []
    num_dontcare = 0
    term.each_with_index {|v, i|
      if v == false
        t << ("!" + input_names_ary[i])
      elsif v == true
        t << input_names_ary[i]
      else # :x
        num_dontcare += 1
      end
    }
    if num_dontcare == term.length
      r << 'true'
    else
      r << t.join('&')
    end
  }
  return "false" if r.empty?
  r.join(' | ')
end

#inspect ⇒ Object

:stopdoc:



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# File 'lib/truthtable.rb', line 57

def inspect
  result = "#<#{self.class}:"
  @table.each {|inputs, output, order|
    term = []
    each_input(inputs) {|name, input|
      if input
        term << name
      else
        term << "!#{name}"
      end
    }
    result << " #{term.join('&')}=>#{output}"
  }
  result << ">"
  result
end

#pretty_print(q) ⇒ Object 



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# File 'lib/truthtable.rb', line 74

def pretty_print(q)
  q.object_group(self) {
    q.text ':'
    q.breakable
    q.seplist(@table, lambda { q.breakable('; ') }) {|inputs, output, order|
      term = []
      each_input(inputs) {|name, input|
        if input
          term << " #{name}"
        else
          term << "!#{name}"
        end
      }
      q.text "#{term.join('&')}=>#{output}"
    }
  }
end

#sort_names(names) ⇒ Object 



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# File 'lib/truthtable.rb', line 105

def sort_names(names)
  total_order = all_names
  names.sort_by {|n| total_order[n] }
end

#to_s ⇒ Object 



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# File 'lib/truthtable.rb', line 24

def to_s
  r = ''
  names = sort_names(all_names.keys)
  format = ''
  sep = ''
  names.each {|name|
    format << "%-#{name.length}s "
    sep << '-' * (name.length+1)
  }
  format << "| %s\n"
  sep << "+--\n"
  r << sprintf(format, *(names + ['']))
  r << sep
  @table.each {|inputs, output, order|
    h = {}
    each_input(inputs) {|name, input|
      h[name] = input
    }
    args = []
    names.each {|name|
      if h.has_key? name
        args << (h[name] ? 't' : 'f').center(name.length)
      else
        args << '?'.center(name.length)
      end
    }
    args << (output ? 't' : 'f')
    r << sprintf(format, *args)
  }
  r
end