> cleverness and hacks often makes code hard > to debug or read particularly when programs grow.
I was really just showing that it could be done. The next step would be to package the subroutine up as a library so that is can be reused. This has been done before in module like Error that gives you constructs that look like typical try/catch/finally. And once it is packaged, and deemed stable, you never have to worry about it again. Just think how often you use a module, and never question that it is working correctly. > i'm not searching a way to solve a single > problem but trying to make programming easier. This is what packaging up the functionality will do. A quick search on CPAN shows several specialized loop constructs that are designed to make programming easier: IfLoop - mixes if and for syntax Proc::ParallelLoop - loop in parallel Loop - for loops with added value Why not add another loop construct module? ...In fact, I challenge you to do so. :) > If loops returned values it would make the > whole coding much clearlier and better > structured - at least i believe so. It sounds like what you are after is to modify the current loop constructs. The issue there is that returning a value for all loops requires extra overhead. Since most users won't want anything returned from a loop you end up just wasting some CPU time. Sure, you might argue that a few CPU cycles won't hurt anyone... but what about the next thing someone wants added, and the next, and the next. I would expect the users that would use such a construct would be few, especially since it isn't a common paradigm, so I think it is better suited as an extension as opposed to a built-in. Rob -----Original Message----- From: Ville Jungman [mailto:[EMAIL PROTECTED] Sent: Thursday, September 25, 2003 10:18 PM To: Hanson, Rob; [EMAIL PROTECTED] Subject: RE: Should loops return a value? >From: "Hanson, Rob" <[EMAIL PROTECTED]> >If you really want a loop to return something, you can roll your own, even >in Perl 5... but the syntax won't be as you gave. Ye - i'm not searching a way to solve a single problem but trying to make programming easier. If loops returned values it would make the whole coding much clearlier and better structured - at least i believe so. It'd b easy to just watch a code and say what it's doing in many cases. Look at what You write below; it is of course clever code but cleverness and hacks often makes code hard to debug or read particularly when programs grow. Yours, --- Ville Jungman >How is this? The only difference is that you need to put the array to loop >over after the code. it's close though. > >sub loop (&@); > >my @x = (1,3,5,7); >my @y = loop { > return $_[0]."a" if $_[0] > 4; >} @x; > >print "@y"; > > >sub loop (&@) { > my $sub = shift; > my @ret; > > foreach (@_) { > my $val = &$sub($_); > push @ret, $val if $val; > } > > return @ret; >} > >Rob > > >-----Original Message----- >From: Ville Jungman [mailto:[EMAIL PROTECTED] >Sent: Thursday, September 25, 2003 9:36 PM >To: Hanson, Rob; [EMAIL PROTECTED] >Subject: RE: Should loops return a value? > > >Rob, did You read my message at all :-) ? > >i just was wandering if there _could_ be more readable way to do this. >Andnot only for to be readable. If loops (and maybe some other builtin >commands, too - we are not talking only about whiles and for's) returned >values, programming might be a way different because you could combine >loops > >with for example those greps and maps. Consider really what would be >possible to do with this (maybe look at those examples again, too, to get >the idea). Also You can not do everything with grep and map and on the >other > >hand they are not very fast to read or debug when comparizing with this. > >i've _always_ wanted to have a program language where loop-commands could >return whatever is needed. It might be that someday i have to write such >language or make a fast poor implementation. If this ability would be >implemented wisely to perl (or to some other language), it wouldn't even >affect to performance (ok, maybe little bit). But it'd bring much power >because You could have more control, readibility and straightforwardity in >Your code - and maybe more speed in some circumstances, too. > >Kindly, Ville Jungman > > >From: "Hanson, Rob" <[EMAIL PROTECTED]> > >@values = (1,3,5,7); > >@bigger_than_4 = map {$_.'a'} grep {$_>4} @values; > >print "@bigger_than_4"; > > > You need to escape a loop with a value. > > > >Not sure I understand what you are trying to accomplish, but this is the > >equivalent of your Perl version and is as short as your proposed syntax. > > > >while (<FH>) { > > next unless /stop/; > > #somthing > > last; > >} > > > >Rob > > > > > >-----Original Message----- > >From: Ville Jungman [mailto:[EMAIL PROTECTED] > >Sent: Thursday, September 25, 2003 8:25 PM > >To: [EMAIL PROTECTED] > >Subject: Should loops return a value? > > > > > >Shortly, I think it might be good if loops (etc.) could return values. > > > > > > > >Example 1: Retnext (like 'return next' borrowed from pl/sql) > >You want to extract numbers from an array if they are > 4 and put an > >'a'-letter after them. > > > > @values=(1,3,5,7); > > @bigger_than_4= # get an array from loop > > foreach $value(@values) { > > retnext $value."a" if $value > 4; # return value from loop if > > > > >4 > > } > > ; > > > > > > > >Example 2: Retlast (== perl 'last'-command with a value) > > > >You need to escape a loop with a value. Familiar way: > > > > while(<FH>){ > > if(/stop/){ > > $array_terminated='true'; > > last; > > } > > } > > if($array_terminated){ > > # something > > } > > > >This could be written as: > > > > if( > > while(<FH>){ > > retlast if /stop/; # returns $_ by default > > } > > ){ > > # something > > } > > > > > > > >So, not very conserverite but think what all you could do with this. > >And please, let me know what you think about this. Crap? > > > >--- > > > >ville jungman, 2 laureston crescent, tower, blarney, cork, ireland > >tel. + 353 - 21 - 451 6847, http://www.kolumbus.fi/vilmak > >usko Herraan Jeesukseen, niin sinä pelastut. (apt. 16:31) > > > >_________________________________________________________________ > >Add photos to your messages with MSN 8. Get 2 months FREE*. > >http://join.msn.com/?page=features/featuredemail > > > > > >-- > >To unsubscribe, e-mail: [EMAIL PROTECTED] > >For additional commands, e-mail: [EMAIL PROTECTED] > > > >-- > >To unsubscribe, e-mail: [EMAIL PROTECTED] > >For additional commands, e-mail: [EMAIL PROTECTED] > > > >_________________________________________________________________ >MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. >http://join.msn.com/?page=features/virus _________________________________________________________________ The new MSN 8: advanced junk mail protection and 2 months FREE* http://join.msn.com/?page=features/junkmail -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
