Prolog - Sicstus: Context error: declaration appeared in query

Author

Sicstus: Context error: declaration appeared in query

Adam Gent

2005-04-06, 12:44 pm

Hi,

I keep getting the error shown below in Sicstus

Context error: declaration appeared in query

When I run the same code under gprolog it works fine and I get the
expected result.

I can not find any reference as to why the above error is created or
how to overcome the error.

I would be grateful if anyone could point me in the right direction.

Thanks,

Adam

Bart Demoen

2005-04-06, 12:44 pm

Adam Gent wrote:
> Hi,
>
> I keep getting the error shown below in Sicstus
>
> Context error: declaration appeared in query
>
> When I run the same code under gprolog it works fine and I get the
> expected result.
>
> I can not find any reference as to why the above error is created or
> how to overcome the error.
>
> I would be grateful if anyone could point me in the right direction.
>
> Thanks,
>
> Adam

You could have given us more of the error message and then we wouldn't
have to guess which declaration you have put in a query ...
But here is something that shows the same message: at the toplevel of
SICStus:

| ?- dynamic(foo/1).
! Context error: declaration appeared in query
! goal: dynamic foo/1

| ?- mode(foo(+)).
! Context error: declaration appeared in query
! goal: mode foo(+)

| ?- meta_predicate(foo(-)).
! Context error: declaration appeared in query
! goal: meta_predicate foo(-)

Enough for you ? Look up the goal part in the manual ...

Cheers

Bart Demoen

Adam Gent

2005-04-06, 12:44 pm

Bart Demoen <bmd@cs.kuleuven.ac.be> wrote in message news:<1112647546.957213@seven.kulnet.kuleuven.ac.be>...
> Adam Gent wrote:
>
> You could have given us more of the error message and then we wouldn't
> have to guess which declaration you have put in a query ...

Hi,

One of the queries that fail is

is_a_module_no(ModuleNumber):-
(
module(ModuleNumber, _)
->
write('Module Exists')
;
write('Module Does Not Exist')
).

when calling is_a_module_no(cmo101).

Part of the module decleration is

module(cmo101, module_details('Maths 101', 'Sally Johnson')).
module(cmo102, module_details('Programming 102', 'Peter Pan')).

Thanks,

Adam

vannoord@let.rug.nl

2005-04-06, 12:44 pm

Adam Gent <adam@misthos.com> wrote:

> One of the queries that fail is

> is_a_module_no(ModuleNumber):-
> (
> module(ModuleNumber, _)
> ->
> write('Module Exists')
> ;
> write('Module Does Not Exist')
> ).

> module(cmo101, module_details('Maths 101', 'Sally Johnson')).
> module(cmo102, module_details('Programming 102', 'Peter Pan')).

Adam,

module/2 has a special role in SICStus (see manual) so you cannot call
any of your binary predicates "module".

Gertjan

--
Gertjan van Noord Alfa-informatica, RUG, Postbus 716, 9700 AS Groningen
vannoord at let dot rug dot nl http://www.let.rug.nl/~vannoord

Bart Demoen

2005-04-06, 12:44 pm

Adam Gent wrote:

> is_a_module_no(ModuleNumber):-
> (
> module(ModuleNumber, _)
> ->
> write('Module Exists')
> ;
> write('Module Does Not Exist')
> ).
>
> when calling is_a_module_no(cmo101).
>
> Part of the module decleration is
>
> module(cmo101, module_details('Maths 101', 'Sally Johnson')).
> module(cmo102, module_details('Programming 102', 'Peter Pan')).

You seemed to have missed what SICStus is so kind to tell you:

* module/2 - NOT redefined

What you wrote was not a module declaration, but facts for a module/2
predicate - and SICStus doesn't like it at all.

Adam Gent

2005-04-06, 12:44 pm

> > One of the queries that fail is
>
>
>
>
>
> Adam,
>
> module/2 has a special role in SICStus (see manual) so you cannot call
> any of your binary predicates "module".

Gertjan,

Thanks you, after I change the module entries it worked fine.

Thanks,

Adam

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