[EMAIL PROTECTED] wrote: > "Jeff Pang" <[EMAIL PROTECTED]> writes: > > >> On Dec 3, 2007 12:51 PM, <[EMAIL PROTECTED]> wrote: >> >>> "Jeff Pang" <[EMAIL PROTECTED]> writes: >>> >>>> mhh? It won't print a newline, it even won't print anything. >>>> b/c @ar is empty, for(...) doesn't go into it, 'print' won't be happened. >>>> >>> Yeah your right... (what was I thinking...) but my point was that it >>> seems perl should say something about this. It seams at least as >>> significant as trying to use an undeclared var. >>> >>> > > >> which value was undeclared? the "$_" one? this is a built-in variable >> in perl, it doesn't need to be declared. >> anyway, you didn't use an undeclared value, so perl won't warn it. >> > > No, no, I didn't make myself clear. I'm saying running into a for > loop array that has no value seems to me to be at least as significant > as running into a variable that is undeclared. But the undeclared var > will invoke a warning while the empty AR in a for loop will not. > > But someone has already answered that Larry Wall and all the perl > devel people have run into many places were choice had to be made > about issuing warning.... The empty for loop didn't make the cut. > > > The for loop is a conditional loop, a derivative of the simpler do/while loops. The syntax makes it a bit harder to recognize it as such, particularly when used in the "foreach" type of test loop rather than the long format. It is therefore more comparable to a conditional that is never true than an undeclared variable. That's misleading in this case, though, since it would often be true, it's more comparable to a standard conditional which I can't imagine you'd expect an error from when it tests false. The flow of the program through conditionals and control structures is a complex and variable enough process that for a computer to accurately warn about it's misuse would likely require that the computer actually understand what you're doing to do.
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