
<ConsistencyModule:> <=>(+ConX,+ConY,Bool)

   Bool is the reified truth of constraint ConX is equivalent to the truth of ConY.

Arguments
   ConX                Constraint
   ConY                Constraint
   Bool                Reified truth value of the constraint (array notation accepted)

Type
   library(gfd)

Description

   Equivalent to BX #= (ConX), BY #= (ConY), Bool #= (BX #= BY)
   
   The two constraints are reified in such a way that Bool is true if ConX
   and ConY have the same truth value.  ConX and ConY must be
   constraints that have a corresponding reified form.

   This reified connective is not available in IC because #=/3 can be 
   used instead. It is provided in GFD as  maps to gecode's 
   equivalence connective. 

   ConsistencyModule is the optional module specification to give the 
   consistency level for the propagation for this constraint: 
   gfd_bc for bounds consistency, and gfd_gac for domain (generalised arc) 
   consistency. 

   This constraint is implemented using Gecode's MiniModel's rel() for
   both integer and boolean expressions, with sub-expressions/constraints
   not supported by MiniModel factored out and posted as auxiliary 
   constraints.

   A more restricted version of this constraint is defined in the 
   global constraint catalog as 'equivalent', in that the reified truth value
   is the logical equivalence of 0/1 variables rather than constraints.



Modules
   This predicate is sensitive to its module context (tool predicate, see @/2).

See Also
   <=> / 2, neg / 2, => / 3, or / 3, xor / 3, and / 3, suspend : #\= / 3, fd : #\= / 3, ic : #\= / 3
