[mercury-users] rule is a reserved word?

[Dominique de Waleffe]

Just got that one a few days ago too. Appears that rule is used for some
purpose in nu-prolog and defined in Mercury as reserved word for
compatibility...

D.

> -----Original Message-----
> From: owner-mercury-users at cs.mu.OZ.AU
> [mailto:owner-mercury-users at cs.mu.OZ.AU]On Behalf Of Gustavo A. Ospina
> Sent: Monday, June 07, 1999 10:46 AM
> To: mercury-users at cs.mu.OZ.AU
> Subject: [mercury-users] rule is a reserved word?
>
>
> Hi. First of all thanks all Mercury team for an really good programming
> language. I'm really in love with it.
>
> I've found a strange error that I want to show with the following code:
>
> %----------------------------------------
> :- module foo.
>
> :- interface.
>
> :- type rule --->
> 	foo1 ; foo2 ; foo3.
>
> :- pred foo(rule, int).
> :- mode foo(in, out) is det.
>
> :- implementation.
>
> foo(foo1, 1).
>
> foo(foo2, 2).
>
> foo(foo3, 3).
> %----------------------------------------
>
> The compiler (version 0.8.1, running on a PC with Windows NT and cygwin
> b20) rejects this with these messages:
>
> bash-2.02$ mmc -c foo.m
> foo.m:005: Syntax error at token 'rule': unexpected token at start of
> (sub)term.
> foo.m:008: In definition of predicate `foo:foo'/2:
> foo.m:008:   error: undefined type `rule'/0.
> For more information, try recompiling with `-E'.
>
> Really I've found this error when I was making a program to implements a
> grammar. I want to define a type 'rule' to represent grammar rules and the
> compiler rejects my module, so I had to change the name to 'regle'.
>
> The unique explanation I see is that 'rule' should be a reserved word. But
> I don't know what is its usage. I would like to know what is the
> real usage
> of the word 'rule' (some pragma? declaration?) or if it's an error.
>
> Best regards and good luck.
>
> + Gustavo.
>
>
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