Re: CLP(FD): what is necessary?

On 2008-03-14, A.L <alewando@xxxxxxxxxx> wrote:
On 14 Mar 2008 13:31:56 GMT, Jan Wielemaker <jan@xxxxxxxxxxxxxxxxxxx>
wrote:

On 2008-03-14, vscosta@xxxxxxxxx <vscosta@xxxxxxxxx> wrote:

Hi!

Well, you have my support :). I'd actually suggest adding a prolog
flag to disable evaluation of generic terms outside eval.

Added. No flag. I just agree this is better style. When Bart&Tom
finish their type checker we can flag the is/2 type errors and people
can wrap the victim variables in eval(Var).

Flags changing runtime behaviour are far more evil than evaluating
terms under is/2 :-)

OK, but what standard says about this? Does it say at all?...

Nothing. Many Prolog systems take the freedom to add more evaluable
functions. This is just one example. If you use it, it will work on
ECLiPSe, SWI-Prolog >= 5.6.53 and if I understand Vitor on the next
YAP release. On most other systems you get an exception. If there is
a good and portable type system for which having eval(_) is useful, it
will eventually get more popular and ISO standard. Dream dream ...

Cheers --- Jan
.

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