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In cleaning up my More wxPerl Examples code in preparation to moving it to github, I came across several examples that use the switch construct. I want to update these to use the given-when construct. As seen below, I got a version to work, but there has to be a simpler/cleaner syntax. It seems to be something to do with (de)referencing the constant.

Thanks in advance, James

wxID_YES, wxID_NO, and wxID_CANCEL are wxPerl constants from use Wx qw(:everything).

Original working construct

use switch; switch ($selection) { case wxID_YES {$self->Wx::LogStatus ("You pressed: \ +"Yes\" ")} case wxID_NO {$self->Wx::LogStatus ("You pressed: \" +No\" ")} case wxID_CANCEL {$self->Wx::LogStatus ("You pressed: \" +Cancel\" ")} }

Replaced switch construct with given-when construct - fails, always takes Yes path

given ($selection) { when (wxID_YES) {$self->Wx::LogStatus ("You pressed: + \"Yes\" ")} when (wxID_NO) {$self->Wx::LogStatus ("You pressed: +\"No\" ")} when (wxID_CANCEL) {$self->Wx::LogStatus ("You pressed: +\"Cancel\" ")} }

Working given-when construct

given ($selection) { when ($_ == wxID_YES) {$self->Wx::LogStatus ("You pre +ssed: \"Yes\" ")} when ($_ == wxID_NO) {$self->Wx::LogStatus ("You pres +sed: \"No\" ")} when ($_ == wxID_CANCEL) {$self->Wx::LogStatus ("You pres +sed: \"Cancel\" ")} }

It also works if the constant is assigned to a scaler and then the scaler is used in the when clause.

my $yes = wxID_YES; when ($yes) {....}

Thanks to Athanasius for the great explanation and test code. I had seen the constant as subroutine construct, but didn't know how it worked in this case(hidden smart match). Thanks also to tobyink. The when ([wxID_YES]) {....} also works (why?) and seems cleaner than what I had come up with. I will go with the bracket construct. Thanks also to Anonymous Monk for the reference to the bug report.


Thanks again to Athanasius and tobyink. The "why?" is now answered very clearly. I had tried when ((wxID_YES)) and when ({wxID_YES}). I guess one more try and I wouldn't have asked the question and I still wouldn't have known why it worked! There are a lot of good teachers out there willing to share their time and knowledge. Thanks!

In reply to converting from switch to given-when by jmlynesjr

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