> Mailing-List: contact [EMAIL PROTECTED]; run by ezmlm > Date: Mon, 18 Nov 2002 18:59:58 -0500 > From: matt diephouse <[EMAIL PROTECTED]> > X-SMTPD: qpsmtpd/0.12, http://develooper.com/code/qpsmtpd/ > > Damian Conway wrote: > >> matt diephouse wrote: > > > >>> $junction = $x | $y | $z; > >>> foo($junction); # Call foo($x), foo($y), and foo($z) > >>> # in parallel and collect the results > >>> # in a disjunction > >> > >> > >> > >> Looking at that code, I'm wondering how you pass a junction. Suppose > >> I want to pass a junction to a subroutine instead of calling the sub > >> with each value of the junction... how would I do that? > > > > > > Tell the sub that it's expecting an undistributed junction as its > > argument: > > > > sub foo($param is junction) {...} > > > > Damian > > Doesn't that go against perl's dynamic philosophy? That requires me to > type my methods where I may not want to. Let's say I have a sub that > logs errors: > > sub log_error($fh, $error) { # filehandle and error msg > $error_num++; # global > print $fh: "$error_num: $error\n"; > } > > my $file = open "error.log"; > log_error $file, "This message is phony"; > > However, during my debugging, I realize that I need two error logs > (Don't ask me why, I just do). Instead of changing the one line to > > my $file = open "error.log" & "../some/other.log"; # I hope this is > legal > > I also need to change the subroutine now, because the error count will > be off, even though my change is temporary. It reduces the ability to > write subs that accept anything and DWIM. The question is when/how do > you choose whether to pass a junction or evaluate all of them. I think > that the solution would be best left out of the sub's signature though. > Of course this has to stop somewhere; you eventually have to pick a state.
It's either that or have your functions, which were perfectly logical suddenly be subject to junction logic. That is, if $x == 2 and $x == 3 both being true, when your code relies on them not both firing. I think it's a very good decision to make sure that functions know they might be getting junctions and making it explicit. Luke > m:att d:iephouse > >
