module Gecode::Util

A module that provides some utility-methods for constraints.

Constants

COMPARISON_ALIASES: Various method aliases for comparison methods. Maps the original (symbol) name to an array of aliases.
NEGATED_RELATION_TYPES: The same as above, but negated.
NEGATED_SET_RELATION_TYPES: The same as above, but negated.
PROPAGATION_KINDS: Maps the name used in options to the value used in Gecode for propagation kinds.
PROPAGATION_STRENGTHS: Maps the name used in options to the value used in Gecode for propagation strengths.
RELATION_TYPES: Maps the names of the methods to the corresponding integer relation type in Gecode.
SET_ALIASES
SET_OPERATION_TYPES: Maps the names of the methods to the corresponding set operation type in Gecode.
SET_RELATION_TYPES: Maps the names of the methods to the corresponding set relation type in Gecode.

Public Instance Methods

constant_set?(expression) click to toggle source

Checks whether the specified expression is regarded as a constant set. Returns true if it is, false otherwise.

# File doc/tmp/rdoc_dev/gecoder/interface/constraints.rb, line 415
def constant_set?(expression)
  return (
     expression.kind_of?(Range) &&        # It's a range.
     expression.first.kind_of?(Fixnum) &&
     expression.last.kind_of?(Fixnum)) ||
    expression.kind_of?(Fixnum) ||        # It's a single fixnum.
    (expression.kind_of?(Enumerable) &&   # It's an enum of fixnums.
     expression.all?{ |e| e.kind_of? Fixnum })
end

constant_set_to_int_set(constant_set) click to toggle source

Converts the different ways to specify constant sets in the interface to an instance of Gecode::Raw::IntSet. The different forms accepted are:

Single instance of Fixnum (singleton set).
Range (set containing all numbers in range), treated differently from other enumerations.
Enumeration of integers (set contaning all numbers in set).

# File doc/tmp/rdoc_dev/gecoder/interface/constraints.rb, line 398
def constant_set_to_int_set(constant_set)
  unless constant_set?(constant_set)
    raise TypeError, "Expected a constant set, got: #{constant_set}."
  end
  
  if constant_set.kind_of? Range
    return Gecode::Raw::IntSet.new(constant_set.first, constant_set.last)
  elsif constant_set.kind_of? Fixnum
    return Gecode::Raw::IntSet.new([constant_set], 1)
  else
    constant_set = constant_set.to_a
    return Gecode::Raw::IntSet.new(constant_set, constant_set.size)
  end
end

constant_set_to_params(constant_set) click to toggle source

Converts the different ways to specify constant sets in the interface to the form that the set should be represented in Gecode (possibly multiple paramters. The different forms accepted are:

Single instance of Fixnum (singleton set).
Range (set containing all numbers in range), treated differently from other enumerations.
Enumeration of integers (set contaning all numbers in set).

# File doc/tmp/rdoc_dev/gecoder/interface/constraints.rb, line 377
def constant_set_to_params(constant_set)
  unless constant_set?(constant_set)
    raise TypeError, "Expected a constant set, got: #{constant_set}."
  end

  if constant_set.kind_of? Range
    return constant_set.first, constant_set.last
  elsif constant_set.kind_of? Fixnum
    return constant_set
  else
    constant_set = constant_set.to_a
    return Gecode::Raw::IntSet.new(constant_set, constant_set.size)
  end
end

decode_options(options) click to toggle source

Decodes the common options to constraints: strength, kind and reification. Returns a hash with up to three values. :strength is the strength that should be used for the constraint, :kind is the propagation kind that should be used, and :reif is the (bound) boolean operand that should be used for reification. The decoded options are removed from the hash (so in general the hash will be consumed in the process).

Raises ArgumentError if an unrecognized option is found in the specified hash. Or if an unrecognized strength is given. Raises TypeError if the reification operand is not a boolean operand.

# File doc/tmp/rdoc_dev/gecoder/interface/constraints.rb, line 339
def decode_options(options)
  # Propagation strength.
  strength = options.delete(:strength) || :default
  unless PROPAGATION_STRENGTHS.include? strength
    raise ArgumentError, "Unrecognized propagation strength #{strength}."
  end
  
  # Propagation kind.
  kind = options.delete(:kind) || :default
  unless PROPAGATION_KINDS.include? kind
    raise ArgumentError, "Unrecognized propagation kind #{kind}."
  end  
                
  # Reification.
  reif_var = options.delete(:reify)
  unless reif_var.nil? or reif_var.respond_to? :to_bool_var
    raise TypeError, 'Only boolean operands may be used for reification.'
  end
  
  # Check for unrecognized options.
  unless options.empty?
    raise ArgumentError, 'Unrecognized constraint option: ' + 
      options.keys.first.to_s
  end
  return {
    :strength => PROPAGATION_STRENGTHS[strength], 
    :kind => PROPAGATION_KINDS[kind],
    :reif => reif_var
  }
end

extract_propagation_options(params) click to toggle source

Extracts an array of the values selected for the standard propagation options (propagation strength and propagation kind) from the hash of parameters given. The options are returned in the order that they are given when posting constraints to Gecode.

# File doc/tmp/rdoc_dev/gecoder/interface/constraints.rb, line 429
def extract_propagation_options(params)
  params.values_at(:strength, :kind)
end