Prolog - Re: Operator ambiguity - was LPTP - was Prolog compiler for Windows XP.

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Re: Operator ambiguity - was LPTP - was Prolog compiler for Windows XP.

Jan Wielemaker

2005-08-10, 9:04 am

On 2005-08-09, Jens Kilian <jjk@acm.org> wrote:
> Jan Wielemaker <jan@nospam.ct.xs4all.nl> writes:
>
> IIRC, there's a rule about atoms which are arguments of operators,
> which would disallow the infix case here.
>
> [time passes]
>
> Ah yes, it should be (I only have an old draft standard) this one:
>
> 6.3.1.3 Atoms
>
> [...] An atom which is an operator shall not be the immediate operand
> of an operator. [...]

Curious sentence. So

:- op(20, fx, aap).

?- display(- aap).
-(aap)

is actually not allowed by the standard? SWI and SICStus allow for it
(and most likely most Prologs).

Cheers --- Jan

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