Stewart Gordon wrote:
Stewart Gordon wrote:Yigal Chripun wrote: <snip>IMO, either the switch statement should remain the low level (effiecient) construct as in C, or replaced by a general mechanism of pattern matching. your solution is kinda between the two above options and I don't see the point of it.What would a "general mechanism of pattern matching" involve, and how would it replace switch? Would it replace if as well?I'd personally prefer pattern matching to be added to D and the switch to be deprecated and eventually removed from the language.I'd personally prefer my proposal from years ago to be taken seriously: http://www.digitalmars.com/d/archives/22722.html ISTM silly to improve switch but at the same time keep it restricted to the same old arcane syntax. Stewart.I have several idea on this, nothing finished though: the only reason for switch in the first place is an optimization in the compiler, besides that, there is no need for it at all and everything can be done with a bunch of if statements. we basically need a way to group several if/case statements together and make them refer the same variable. here's a first attempt: match (value) { case(1) foo(); case(2..4) { foo(); case(3) foo3(); bar(); continue; } case(5) {...} case() {...} // this is the default case }So you make the () required so that the {} can be optional. At least it's consistent with most other control flow statements this way. I'm not sure why you need to use up another keyword for this - switch would work fine. At least, I don't think it would lead to any parsing ambiguity, though it might take quite a bit of lookahead to determine which switch syntax is being used. Would continue jump straight into the next case block that is a sibling of the current one, whatever it may be, or what? And where there are uncased statements at the same block level as cased statements, under what circumstances will they be executed? Moreover, will "default" still be legal in place of "case()"? Stewart.
like I said, this is just my first attempt... to answer your questions:1) new keyword is like you said - to prevent ambiguity, but if the compiler can use "switch" without any parsing dificulties than I'm all for utilizing "switch". 2) requiring () is more consistent with the rest of D - const(..), cast(..), etc... also, this way as you noted, the {} are optional 3) continue should be consistent with loops, so it'll jump to next case in list - like current switch fall-through, (similar to 'continue' to next iteration in loop) and if you nest cases or want to skip a case than you can add a label and continue to that label as well. 4) I'm not sure about 'default' isn't it a waste to make it a keyword just for this? is it used anywhere else in the language? 5) i'm unsure about uncased statements - does it make sense to prohibit those? 6)another thing is adding ability to decompose stuff like in FP, for example:
match (arr) { // dynamic array
case([a, b]) { use a, b here } // match if array has two elements
...
}
