[m-dev.] logging proposal

[Ian MacLarty]

On 1 Mar 2006, at 23:25, Ralph Becket wrote:

> Ian MacLarty, Wednesday,  1 March 2006:
>>
>> I would argue for using a higher-order term.  Anything complex should
>> probably be defined in another predicate anyway (you don't want your
>> predicate bodies littered with long debug goals).
>>
>> The thing that bothers me about the 'debug [!IO] (...)' syntax is that
>> there are always only two variables in the square brackets and square
>> brackets are normally used for arbitrary length lists.  Perhaps it
>> should be 'debug {!IO} (...)'?
>>
>> I favor the ho term approach, but I don't feel strongly about it.
>
> I think the HO approach is a pretty awful idea.  Compare
>
> 	debug [!IO] (
> 		io.see("logfile", _, !IO),
> 		io.print("logmessage", !IO),
> 		io.seen(!IO)
> 	)
>
> with
>
> 	debug (
> 		pred(IO0::di, IO::uo) is det :-
> 			some [!MyIO] (
> 				!:MyIO = IO0,
> 				io.see("logfile", _, !MyIO),
> 				io.print("logmessage", !MyIO),
> 				io.seen(!MyIO),
> 				IO = !.MyIO
> 			)
> 	)
>

Well I would put that in a separate predicate and use currying :-)

> I hear what you're saying, but I think Mark's suggestion is a good
> compromise.  After all, this is intended for debugging work and if
> you make it awkward to use, people will just use the unsafe module
> and compile without optimisation to prevent unsafe.print etc. from
> being optimised away.
>

Okay.  As I said I have no strong feelings on the syntax (as long as it 
doesn't look like a regular predicate call).

Ian.

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