On 2006-11-10 at 00:32+0100 Udo Stenzel wrote:
Jon Fairbairn wrote:
But not all patterns deserve names. To give a reductio-ad-absurdam sort of analogy, suppose someone looked at a lot of C and came to the conclusion that “for (i=0, i++, ...)” occurred in 90% of programmes. Were they to reason that it would be worth #defining a macro FORI(...) and using that instead, I suspect that the suggestion would be roundly dismissed.
Well, I presume you actually meant 'for( i=0; ... ; i++ )', an error which would have been avoided by using a macro.
If I don't know the order of the clauses in C loops, a macro isn't going to help much: I shouldn't programme in C full stop. Fortunately I don't, so that's OK. Unless you are seriously arguing that embedding the name of the loop control identifier in a macro is a good idea, it seems I pared down my "obviously silly" example to the point where the sillyness was no-longer obvious. I was trying to be too concise. I meant to say that "If someone found that 90% of control variables are called “i”, that wouldn't make it a good idea to have a macro “FORi” that expanded into “for (i,...)”" -- the incrementing by one was incidental.
Also, a macro would have liberated you of the choice between '++i' and 'i++', where '++i' is often more efficient (at least in C++). And in C++, you're encouraged to use std::for_each anyway, which is the C++ way to spell 'mapM_'. Which would make your point kinda moot, but I'm not really convinced that arguments from a souped up assembly language can be used to make a point about Haskell.
Evidently not. C is so clumsy that I messed up my trivial and silly example completely.
Of course not, but you have to be careful what you deduce from the old code, particularly if you are reasoning from "most code is like this", because that doesn't tell you whether most code should be like that or most code should have been written differently.
Exactly! To state it explicitly: it seems, 'intersperse' is either used at type 'String' or in conjunction with pretty printing. Or in other words, either with pretty printing or with ugly printing. Therefore, the right thing to do is not to provide an ugly printing idiom, but to improve Text.PrettyPrint to the point where it is easier to use than plain strings.
Right. If there is a problem, I don't think it's that “intercalate foo” is currently spelled “concat . intersperse foo”, and if there is something deeper we can do to mend the problem, I'm in favour of it. Actually, I'd start by deprecating Show, because for machine readability it's not efficient and for human readability it's too simplistic. Jón -- Jón Fairbairn Jon.Fairbairn at cl.cam.ac.uk