Class: Gecode::Constraints::IntEnum::Element::ExpressionStub

Inherits:
Gecode::Constraints::Int::CompositeStub show all
Defined in:
lib/gecoder/interface/constraints/int_enum/element.rb

Overview

Describes a CompositeStub for the element constraint, which places a constraint on a variable at the specified position in an enumeration of integer variables. It’s basically the array access of constraint programming.

Example

# The variable at the +x+:th position in +int_enum+ must be larger than
# +y+.
int_enum[x].must > y

# The price of +selected_item+ as described by +prices+ must not be 
# larger than 100.
prices = wrap_enum([500, 24, 4711, 412, 24])
prices[selected_item].must_not > 100

# Reify the constraint that the +x+:th variable in +int_enum+ must be in 
# range 7..17 with the boolean variable +bool+ and select strength 
# +domain+.  

int_enum[x].must_be.in(7..17, :reify => bool, :strength => :domain)

Instance Method Summary collapse

Methods inherited from Gecode::Constraints::Int::CompositeStub

#initialize

Methods inherited from CompositeStub

#initialize

Methods included from LeftHandSideMethods

#must, #must_not

Methods inherited from ExpressionStub

#initialize

Constructor Details

This class inherits a constructor from Gecode::Constraints::Int::CompositeStub

Instance Method Details

#constrain_equal(variable, params, constrain) ⇒ Object 



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# File 'lib/gecoder/interface/constraints/int_enum/element.rb', line 25

def constrain_equal(variable, params, constrain)
  enum, position = @params.values_at(:lhs, :position)
  if constrain
    variable.must_be.in enum.domain_range
  end
  
  # The enum can be a constant array.
  enum = enum.to_int_var_array if enum.respond_to? :to_int_var_array
  Gecode::Raw::element(@model.active_space, enum, 
    position.bind, variable.bind, *propagation_options)
end