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);

[download]

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);

[download]

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

[download]

Which is actually code I see right now. Yuck! That can't be right - can it?

Bye
 PetaMem     All Perl:   MT, NLP, NLU

In reply to Getopt::Long defaults for options with multiple values by PetaMem

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.