[gecode-users] posting of expressions

[Kish Shen]

Christian Schulte wrote:
> Hi Kish,
> 
> There is one more thing that might be valuable to you: we have changed the
> way how to post expressions and relations for the upcoming 3.4.0 (which
> should be available end of this month at the latest). 
> 
> It is way more powerful (including arbitrary arithmetic expressions, set
> variables, and so on) and distinguishes between a function expr() that posts
> an expression (and hence returns a variable) and a function rel() that posts
> a relation (and hence does not return a variable). This removes the
> reification operator ~ and the confusion it caused.
> 

Hi Christian,

Thanks for the info. Hmm...much of the reorganisation of the code I 
mentioned was to handle the general expressions allowed in ECLiPSe (or 
more precisely, the ic/fd libraries), to separate out non-linear 
components and reifiable constraints (ic allows (reifiable) constraints 
to occur in expressions and simply use the reified value of the 
constraint in the expression). [The aim is to make the ECLiPSe Gecode 
interface as source compatible to the ic library as possible]

I am not certain if I know what the reification operator is -- is this 
the ~ used in BoolExpr to reify LinRel? I currently use this in 
BoolExpr, but are you suggesting other constraints can be reified with 
this? Am I correct in think for integer finite domain, only LinRel and 
the dom constraints are currently reifiable? These are the only cases I 
am handling in expressions at the moment (and I am currently posting an 
extra reified dom constraint and using its boolean variable in the 
BoolExpr).

Cheers,

Kish


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