Getopt::Long defaults for options with multiple values

PetaMem has asked for the wisdom of the Perl Monks concerning the following question:

Reviewing some middle-aged code, I stumbled across this topic...

Unfortunately, the G:L documentation is silent about default values for options with multiple values: Options-with-multiple-values of Getopt::Long. Even more unfortunate seems an inconsistency compared to defaults for options with single values and maybe a semantic inconsistency at all. If you have a single value option, you may define a default like:

my $tag = 'foo';       # option variable with default value
GetOptions ('tag=s' => \$tag);
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This works as expected. Good. You can - of course - do a similar thing for options that take multiple values:

my $listref = ['a','b','c'];       # option variable with default valu
+es
GetOptions ('list=s{,}' => $listref);
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If you omit the -list option, the program will have the default value, which is good. If you, however, will give a list option, G:L seems to push that option to the list already given in default, which may have its applications, but is not that great as default behavior. If you want to actually replace the default given, you would have to define defaults the ugly, backward and programmatically DIY way:

my $listref = [];       # no default
GetOptions ('list=s{,}' => $listref);
my $listref = @{$listref} ? $listref : ['a', 'b', 'c']; # DIY default
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Which is actually code I see right now. Yuck! That can't be right - can it?

Bye
PetaMem All Perl: MT, NLP, NLU

Comment on Getopt::Long defaults for options with multiple values Select or Download Code

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Re: Getopt::Long defaults for options with multiple values by fishmonger (Chaplain) on Nov 21, 2014 at 15:30 UTC
You can use a subroutine reference and pass a comma separated list to accomplish your goal. `my @list = qw( a b c ); GetOptions ('list=s{,}' => \&list); print Dumper \@list; sub list { # action at a distance # modifies the file scoped @list array @list = split /,/, $_[1]; }` [download] test without passing any arg: `C:\test>list_test.pl $VAR1 = [ 'a', 'b', 'c' ];` [download] test passing arg list: `C:\test>list_test.pl -list d,s,4,f,"test string" $VAR1 = [ 'd', 's', '4', 'f', 'test string' ];` [download]	[reply] [d/l] [select]
Re: Getopt::Long defaults for options with multiple values by toolic (Bishop) on Nov 21, 2014 at 13:26 UTC
Unfortunately, the G:L documentation is silent about default values for options with multiple values If you believe the documentation can be improved, please do so via perlbug. Also note this: Warning: What follows is an experimental feature.	[reply]
Re: Getopt::Long defaults for options with multiple values by Anonymous Monk on Nov 21, 2014 at 13:13 UTC
I don't have any suggestion; only want to note that working with an array is ever so slightly less bothersome than working with an array reference.	[reply]


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