On 11/21/2013 10:06 AM, Martin Schreiber wrote: > that semantic is independent of order of items. With variable case > labels this is not possible.
I don't understand what you mean by this. Could you give an example ? Of course non-constants lead to additional logical problems. If a case label in fact is a function call, it could have side-effects that affect the selection of the other candidates. But this is true for many other syntax elements, as well. E.g. boolean operands are not evaluated if not necessary: function b: Boolean; function c: Boolean var a : Boolean a := b and c; Here, c might have a side effect but is not (necessarily) evaluated if the result of b is false. (At least this is how I understand most syntax definitions are done: evaluation from left to right.) This this user code is erroneous if c has side effects. Moreover in case of site effects the statements a := b and c. and a := c and b. are not equivalent. (Obviously again: This this user code is erroneous if b or c have side effects. ) Same of course holed for case: it is to be evaluated from left to right (i.e. from top to bottom). For me, the "case a of" syntax should be just an abbreviation of an "else if" cascade of if a=x1 then begin ... end else if a = x2 then begin ... end else if a = x2 then begin ... else begin end; In what low level operations this results is up to the compiler optimizations. (Martin: Happy coding ! :-) ) If there are side-effects within the evaluation of the decision-terms, is is obviously possible that some re not evaluated. The compiler needs to be able to rely on this fact and thus any user code that violates this rule needs to be considered as erroneous (see the boolean example above). Of course the order of the blocks might change the behavior. Either the compiler needs to take this into account, or it needs to be defined that any user code that relies on the order needs to be considered (and documented) as erroneous (see the boolean example above) -Michael ------------------------------------------------------------------------------ Shape the Mobile Experience: Free Subscription Software experts and developers: Be at the forefront of tech innovation. Intel(R) Software Adrenaline delivers strategic insight and game-changing conversations that shape the rapidly evolving mobile landscape. Sign up now. http://pubads.g.doubleclick.net/gampad/clk?id=63431311&iu=/4140/ostg.clktrk _______________________________________________ mseide-msegui-talk mailing list mseide-msegui-talk@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mseide-msegui-talk
