[gecode-users] posting of expressions
Christian Schulte
cschulte at kth.se
Tue Jul 13 17:42:29 CEST 2010
Hi Kish,
No, it is as you say, ~ only works in the context of posting linear
relations. This will disappear.
I just attach a draft of the chapter that explains it (even though the
structure is now totally misleading).
Christian
--
Christian Schulte, web.ict.kth.se/~cschulte/
-----Original Message-----
From: Kish Shen [mailto:kisshen at cisco.com]
Sent: Tuesday, July 13, 2010 5:30 PM
To: cschulte at kth.se
Cc: 'Guido Tack'; users at gecode.org
Subject: Re: [gecode-users] posting of expressions
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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