I have multiple views on this "category" of inquiry: I think only an engineer at RocketSoftware can answer this question.
Some people actually use the non-optimization to their benefit. They count on the fact that the expression will be evaluated on every iteration, whether it's a DCount, Field, or some other calculation. Changing this could break applications. Evaluation of expressions might be dynamic - they might only re-evaluate if they need to. The BASIC runtime could setup a dirtyFlag on loops with an expression as an operand. If any component of the expression changes, set the flag. Next time through the iterator check the dirtyFlag. If it's set, then the expression must be re-evaluated, else use the previous value. However, a new problem here is that now there is a special check being set on every variable assignment, which can be a performance issue in itself. More variables involved in the expression means more runtime checks and performance can become worse than if it were just re-evaluating the one expression on every loop. This falls into the category of "be careful what you wish for, you may get it". My bottom line is that we should strive for more options to define and override behaviors like this. We should have the option to make code behave as we expect, using compiler directives - and if a developer doesn't understand the options they're using, that's their problem, not a platform issue. THAT is what we should ask for when looking for features. It's not so much "how it works", but knowing if it's possible to change behavior so that the runtime processes our code the way we want. Tony Gravagno Nebula Research and Development TG@ remove.pleaseNebula-RnD.com Nebula R&D sells mv.NET and other Pick/MultiValue products worldwide, and provides related development services http://Nebula-RnD.com/blog Visit http://PickWiki.com! Contribute! http://Twitter.com/TonyGravagno http://groups.google.com/group/mvdbms > From: Peter Cheney > Does a DCOUNT get evaluated again for each iteration of a loop? > Or is UniVerse these days intelligent enough to keep track of what's > going on? > > e.g. > > for i = 1 to dcount(array,@fm) > *commands here > next i > > versus > > totalattributes = dcount(array,@fm) > for i = 1 to totalattributes > *commands here > next i > > Apart from readability and perhaps easier debugging is there an actual > internal difference? > I know it was an issue on older pick releases but I cannot remember if > it ever affected UV? _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users
