in reply to Re: Correct idiom for default parameters
in thread Correct idiom for default parameters

Ack! 5.8.8 here (sigh).

Thanks for the suggestion though.

  • Comment on Re^2: Correct idiom for default parameters

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Re^3: Correct idiom for default parameters
by BrowserUk (Patriarch) on Apr 28, 2010 at 19:00 UTC

    This is 5.8 accessible and might even be more palatable?

    Updated per LanX's correction below. 

    sub test{ 
    my( $p1, $p2, $p3) = map{ scalar @_ ? shift : $_ }( 1, 2, 3 ); 
    print "p1:$p1; p2:$p2; p3:$p3"; 
};;

test();;
p1:1; p2:2; p3:3

test( 'a' );;
p1:a; p2:2; p3:3

test( 'a', 'b', 'c' );;
p1:a; p2:b; p3:c

    [download]
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]
      careful!

      passing undef in between will break your idiom.

      IMHO better check scalar @_ or care explicitly about passing undef !

      sub defaults { 
    my( $p1, $p2, $p3) = map{ defined $_[0] ? shift : $_ }( 1, 2, 3 );
+ 
    print "p1:$p1; p2:$p2; p3:$p3\n"; 
}; 
 
defaults(undef, 0, 0);

      [download]

      Cheers Rolf

[reply]
[d/l]
[select]

        Sorry, I don't follow?

        Passing undef gives exactly the effect I would expect and desire. That of accepting the default for that parameter: 

        test( 'a', undef, 'c' );;
p1:a; p2:2; p3:c

        [download]
        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]

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