in reply to Re^2: Tutorial RFC: Guide to Perl references, Part 1
in thread Tutorial RFC: Guide to Perl references, Part 1

Yes, I did find it on Perlmonks, and yes please if you have not already done it, I would speak in support of including the other 4. Like others, this description helped a good deal. You reminded me of the "cast" syntax of %{ $ref } and others.

Because the reference looks like a plain scalar, e.g., $starwars one might be tempted to do arithmetic on it (in a module far, far away). $starwars += $Lucas

I use subroutine signatures when I can. Is there a way to require a reference in the signature? Is this in one of the later parts of your documentation?

I currently name the variable with a _ref at the end of the name as a reminder, e.g., $starwars_ref

Reading ahead, I now see that you use _aref, _href, _oref,and _sref.

Thank you, stevieb

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Re^4: Tutorial RFC: Guide to Perl references, Part 1
by AnomalousMonk (Archbishop) on Jul 06, 2017 at 23:06 UTC
    ... is there a way to require a reference in the signature?

    The  \@ \% \& prototypes cause references to the given types of data to be taken and passed to a subroutine. In a sense, you can say this is "requiring a reference." 

    c:\@Work\Perl\monks>perl -wMstrict -le
"sub foo (\%\@) {
   my ($hashref, $arrayref) = @_;
   ;;
   print ref $hashref;
   print ref $arrayref;
   ;;
   print qq{spanish for 'two' is '$hashref->{two}'};
   print qq{@{ $arrayref }};
   }
 ;;
 ;;
 my @ra   = qw(fee fie foe fum);
 my %hash = qw(one uno  two dos  three tres);
 ;;
 foo(%hash, @ra);
"
HASH
ARRAY
spanish for 'two' is 'dos'
fee fie foe fum

    [download]
    (See what happens if you use a hash in place of an array, etc.)

    Of course, in a call to a "normal" (i.e., unprototyped) function like  no_proto(%hash, @array) all the elements of the hash(es) and array(s) would be "flattened" in the function argument list, and there would be no way of telling where one left off and the next began.

    I use subroutine signatures when I can ...

    I can understand why someone who comes from a background in C, C++ or other strongly typed language would feel very comfortable with Perl Prototypes, and think that they understood them as soon as they saw them. I certainly did. But Perl prototypes are a different beast, and in time you may see your sense of understanding and comfort melt away. Please see Far More than Everything You've Ever Wanted to Know about Prototypes in Perl -- by Tom Christiansen for a number of reasons not to use prototypes on a regular basis, but only in rather specialized circumstances — where they can, indeed, sometimes be very useful!

    Give a man a fish:  <%-{-{-{-<

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      Prototypes and signatures aren't the same thing, see Use v5.20 subroutine signatures by brian d foy. 
      ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

      [download]
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