Class: AdaTruthy::TruthTable

Inherits:
Object
  • Object
show all
Defined in:
lib/ada_truthy/truth_table/truth_table.rb

Constant Summary collapse

MAX_LIMIT = 
6
MIN_LIMIT = 
2
SELF = 
'S'
COMPLEMENT = 
'C'
TRUE_VALUE = 
'T'
FALSE_VALUE = 
'F'
@@letters = 
%w[A B C D E F G H I J]
@@combinations = 
{
  2 => 04, 3 => 8, 4 => 16,
  5 => 32, 6 => 64, 7 => 128,
  8 => 256, 9 => 512, 10 => 1024
}

Instance Method Summary collapse

Constructor Details

#initialize(number_of_terms) ⇒ TruthTable

Returns a new instance of TruthTable.



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# File 'lib/ada_truthy/truth_table/truth_table.rb', line 21

def initialize(number_of_terms)
  case number_of_terms
  when number_of_terms > MAX_LIMIT
    raise TruthyException, "The maximum number of terms is #{MAX_LIMIT}"
  when number_of_terms < MIN_LIMIT
    raise TruthyException, "The minimum number of terms is #{MIN_LIMIT}"
  end

  @number_of_terms = number_of_terms
  @number_of_combinations = @@combinations[number_of_terms]

  @cache = Hash.new
  @formula = Array.new
  @rows = Array.new

  @using_sum_of_products = true
  @using_product_of_sums = false

  @number_of_zeros = 0
  @number_of_ones = 0
end

Instance Method Details

#add_row(*terms) ⇒ Object 



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# File 'lib/ada_truthy/truth_table/truth_table.rb', line 43

def add_row(*terms)
  table_has_enough_rows = @rows.size == @number_of_combinations

  if table_has_enough_rows
    raise TruthyException, "There should be only #{@number_of_combinations} rows."
  end

  right_number_of_terms = terms.size == @number_of_terms + 1

  unless right_number_of_terms
    raise TruthyException, "There should be only #{@number_of_terms} terms."
  end

  row = terms

  unless row_is_valid? row
    raise TruthyException, "The combination #{row} has been used already."
  end

  @cache = {}

  row_output = row[-1]
  change_algorithm = (@rows.size == 0).and(row_output == 0)

  use_product_of_sums if change_algorithm

  @rows << row
  (row_output == 1) ? @number_of_ones += 1 : @number_of_zeros += 1

  compute row
end

#check(*terms) ⇒ Object 



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# File 'lib/ada_truthy/truth_table/truth_table.rb', line 75

def check(*terms)
  has_right_number_of_terms = terms.size == @number_of_terms

  unless has_right_number_of_terms
    raise TruthyException, "There should be only #{@number_of_terms} terms."
  end

  change_algorithm_if_needed

  cache_code = TruthTable.get_row_cache_code terms
  cache_result = @cache[cache_code]

  return cache_result unless cache_result.nil?

  terms_cursor = 0
  partial_result = true
  result = false

  if @using_product_of_sums
    partial_result = false
    result = true
  end

  @formula.each do |t|
    if @using_sum_of_products
      partial_result = (t == SELF ? partial_result.and(terms[terms_cursor]) :
                          partial_result.and(!terms[terms_cursor]))
    else
      partial_result = (t == SELF ? partial_result.or(terms[terms_cursor]) :
                          partial_result.or(!terms[terms_cursor]))
    end

    terms_cursor += 1
    next if terms_cursor != @number_of_terms
    terms_cursor = 0

    if (@using_sum_of_products)
      return true if partial_result
      result = result.or(partial_result)
      partial_result = true
    else
      return false if not partial_result
      result = result.and(partial_result)
      partial_result = false
    end
  end

  @cache[cache_code] = result
  return result
end

#to_s ⇒ Object 



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# File 'lib/ada_truthy/truth_table/truth_table.rb', line 126

def to_s
  terms_cursor = 0
  partial_result = ''
  result = ''

  @formula.each do |t|
    if @using_sum_of_products
      partial_result += (t == SELF ? "#{@@letters[terms_cursor]}." : "~#{@@letters[terms_cursor]}.")
    else
      partial_result += (t == SELF ? "#{@@letters[terms_cursor]}+" : "~#{@@letters[terms_cursor]}+")
    end

    terms_cursor += 1
    next if terms_cursor != @number_of_terms
    terms_cursor = 0

    result += (@using_sum_of_products ? "(#{partial_result[0...-1]})+" : "(#{partial_result[0...-1]}).")
    partial_result = ''
  end

  result[0...-1]
end