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[Caml-list] kprintf with user formatters
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Date: | 2004-07-16 (06:18) |
From: | Pierre Weis <pierre.weis@i...> |
Subject: | Re: [Caml-list] kprintf with user formatters |
> On Thu, 15 Jul 2004, Basile Starynkevitch [local] wrote: > > I don't understand what this zprintf function should be, > > It should parse the format string, and ignore format arguments following > it. > > > but the above > > log proposal behave strangely (and perhaps unsafely) : > > > > # log false "a=%d s=%S\n%!" 1 "xyz";; > > - : unit = <unknown constructor> > > The reason for this is that it returns a function and not a unit value. > Unless you parse the format string, there is no way you can know when > to stop eating arguments to return a value. That's the debugger view of the problem :) The Caml compiler's view is simpler: you broke the type system, you get wrong results! > I don't think that this hack will be too dangerous. You might get an > exception 'Invalid_argument "equal: functional value"' if you want to > compare those fancy unit-values, which is about the worst thing you > can achieve. But who would want to compare unit-values anyway? I have no time to try and find a way to get a bus error with that one but I would not be glad to use software based on such a ugly hack that is not proved harmless in any case. > > For what it's worth, long time ago, I ended writing a camlp4 extension > > for a similar logging (or tracing purpose) see file README.trace and > > pa_trace.ml of > > http://cvs.sourceforge.net/viewcvs.py/poesia/PoesiaSoft/PoesiaMonIcap/ > > The preprocessor is not good enough for me. I would like to change > log levels at runtime, because the application is a server which should > run permanently. ``the application is a server which should run permanently'' ? Wao! May I suggest no to use Obj.magic too often for this kind of application ? Especially when you ``don't think that this hack will be too dangerous'': this hack could kill your server not too permanently! Best regards, Pierre Weis INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/ ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners