On Thursday 15 February 2007 14:46, Daniël Mantione wrote: > Op Thu, 15 Feb 2007, schreef Vinzent Hoefler:
> Because, in a case statement you are already "inside" the brackets: Yeah, I sort of figured that. ;) > > Another oddity would be a for loop: > > > > for Bla := One to Five do ... > > > > would be a range only, yes? (Apart from the fact that - due to the > > "to" keyword - really isn't). > > It is a range, but one also needs to specify the direction > (to/downto), so it is logical that for-loops don't use .. syntax. Oh, right, I forgot that. Damn. That's why in Ada you can write for Bla in X'Range loop vs. for Bla in reverse X'Range loop for the intended direction of the given range. > > What about a compiler built-in like Low() and High() called Range() > > where its return type indicates something that would be compatible > > to a case and for label and just denote the range of the whole > > type? > > > > Basically a short cut to the "Low (Type) ..|to High (Type)" > > expression, but without the possible pitfall of writing > > > > Low (Type) .. High (A_Similar_And_Unfortunately_Compatible_Type) > > > > and thus being less error-prone...? > > It looks okay, but does this pitfall actually exist? Yes, it does. Especially when copying and pasting. ;) The reason why I stumbled over that was that I changed a case statement from a perfect fit: case Frequency of 1600: Idx = Hz_1600; ... where the returned Idx is an index to an array of hardware parameters to generate that frequency. For some unpublishable reason I changed that from a perfect match (here: 1600) to a range (say: 1500 .. 1700) and I started declaring range types for that because putting in the range into the case label seemed too bad for later changes. So then I ended up writing: case Frequency of Low (Range_1_6_K) .. High (Range_1_6_K) : Idx := ... Low (Range_1_8_K) .. High (Range_1_8_K) : Idx := ... ... for quite some values. Of course you start copy- and pasting things then and I had to triple check if I really matched the Low(...) with the according High(...) parts and the correct value for Idx. > low(colour)..high(wind_direction) would be a type violation. Yes. But integer ranges are compatible in any case and that's what I am bound to here (in fact, the code even "kind of" changes those integers to a type-safe enumeration type for further uses). > > or > > > > |case Bla in > > |Range (X): ... > > > > doesn't actually look unreadable to me... > > Indeed, but do you solve a problem? I.e. I can imagine some kind of > syntax to allow set constants would help, but this seems mostly a > typing shortcut. Well, it is. The above mentioned lines of Ada code can still be expressed as for Bla in [reverse] X'Low .. X'High loop and would still mean the same. And due to the fact that in Pascal such a Range() built-in would still not be useable in a for loop, it seems, its use would be too limited to be considered an improvement. Unless I'd get Reverse_Range(), too. ;) Regards, Vinzent. _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
