[mercury-users] Re: State variable problem

[Nicholas Nethercote]

On Wed, 31 May 2006, Ralph Becket wrote:

>> Oh, I see:  you're not allowed to use !Errs in a function application.
>
> Yes, state vars in function applications == very odd.

Why is that?  The manual says 
(http://www.cs.mu.oz.au/research/mercury/information/doc-latest/mercury_ref/State-variables.html#State%20variables):

   !X may not appear as an argument in a function application since this
   would not make sense given the usual interpretation of state variables and
   functions.

which doesn't explain much.  In Mercury I think of predicates and functions 
being basically the same except for syntax (cue horrified gasps from more 
knowledgeable members of the audience), but I guess there's something deeper 
than that here.

Also, it would be nice if the error message was a little clearer when you 
try to do this.

Nick
--------------------------------------------------------------------------
mercury-users mailing list
post:  mercury-users at cs.mu.oz.au
administrative address: owner-mercury-users at cs.mu.oz.au
unsubscribe: Address: mercury-users-request at cs.mu.oz.au Message: unsubscribe
subscribe:   Address: mercury-users-request at cs.mu.oz.au Message: subscribe
--------------------------------------------------------------------------