[gecode-users] If then type constraints

[Malcolm Ryan]

If I use reification like this, do I have to write my search code so  
that it instantiates all the booleans as well as all the 'normal'  
variables? Or can I rely on the fact that once all the 'normal'  
variables are instantiated all the booleans should also be instantiated.

Malcolm

On 06/03/2008, at 4:15 PM, Christian Schulte wrote:

> Use reification, that's clumsy but works. So, with minimodeling  
> support it
> should be something like (~ reifies a linear relation, && is  
> conjunction,
> imp is implication, and tt means that the statement must be true):
> 	post(home, tt(imp(~(v1 == 2),~(v2 != 1) && ~(v3 != 3)));
> or directly:
> 	BoolVar b1(home,0,1), b2(home,0,1), b3(home,0,1), b23(home,0,1);
> 	rel(home, v1, IRT_EQ, 2, b1);
> 	rel(home, v2, IRT_NQ, 1, b2);
> 	rel(home, v3, IRT_NQ, 3, b3);
>      rel(home, b2, BOT_AND, b3, b23);
> 	rel(home, b1, BOT_IMP, b23, 1);
>
> Or check whether extensional constraints work for you.
>
> Christian
>
> --
> Christian Schulte, www.ict.kth.se/~cschulte/
>
>
> -----Original Message-----
> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On  
> Behalf
> Of Debdeep Banerjee
> Sent: Thursday, March 06, 2008 3:03 PM
> To: users at gecode.org
> Cc: users at gecode.org
> Subject: [gecode-users] If then type constraints
>
> Hi,
> How do I model if-then style constraints ? What I want to do is post
> constraints if a variable is assigned a particular value. For example
> say  I have variable set V { v1, v2, v3} and each of them has the  
> domain
> {1,2,3}. what I want to achieve is
>    if  v1== 2  then
>         v2 !=1  /\  v3 !=3
>
> I know I can do this using a custom propagator, but is there any  
> other way ?
>
> With regards
> Debdeep
>
> -- 
> Debdeep Banerjee
> PhD Candidate
> CSL/RSISE/NICTA
> Australian National University
> Email: debdeep.banerjee at rsise.anu.edu.au
> Web:http://rsise.anu.edu.au/~banerjed
>
>
>
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