Re: Rosetta Dispatch Table

Why create your own dispatch table when perl has one built in?

Or - violating specifications for fun? and profit?

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1203952

use strict;
use warnings;

# Callback functions ---------------------------------------

sub first::callback {
   my $z = pop;
   print "in first_callback, z=$z\n";
   return 1;
}

sub last::callback {
   my $z = pop;
   print "in last_callback, z=$z\n";
   return 2;
}

sub UNIVERSAL::callback { -1 }

# Implementation of dispatch table -------------------------
# (You need to write this code)

#my %op_table = ( first  => \&first_callback,
#                 last   => \&last_callback,
#               );

sub invoker
{
   my ($name, $z) = @_;
   $name->callback($z);
}

# Main program for testing ---------------------------------

for my $name ( "first", "last", "fred" ) {
   my $rc = invoker( $name, $name . '-arg' );
   print "$name: rc=$rc\n";
}
[download]

Have I once again managed to fail an interview?

Comment on Re: Rosetta Dispatch Table Download Code

Replies are listed 'Best First'.
Re^2: Rosetta Dispatch Table by eyepopslikeamosquito (Archbishop) on Nov 21, 2017 at 23:29 UTC
That's the sort of ingenuity and inventiveness I was hoping to provoke. Thanks. Have I once again managed to fail an interview? I think we both know I would be delighted to offer you a job without requiring an interview ... though I understand you are no longer looking. :)	[reply]
Re^2: Rosetta Dispatch Table by LanX (Saint) on Nov 22, 2017 at 16:53 UTC
some annotations: I would be cautious about name spaces like `first::` and `last::` , if you really need extra packages I'd use an extra parent one like `callback::first` etc I'd use ->can beforehand to check if the callback is really available, to avoid an unexpected die without good notice the STASH - your built in dispatch table - is a hash , just global (which leads to the first remark :) Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^3: Rosetta Dispatch Table by tybalt89 (Monsignor) on Nov 26, 2017 at 18:45 UTC
Is there a case that ->can is needed that is not caught by UNIVERSAL::callback ?	[reply]
Re^4: Rosetta Dispatch Table by LanX (Saint) on Nov 26, 2017 at 20:36 UTC
The code you've shown does only handle methods. ->can does also handle normal subs. Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Wikisyntax for the Monastery}	[reply]
Re^4: Rosetta Dispatch Table by shmem (Chancellor) on Nov 26, 2017 at 19:26 UTC
Is there a case that ->can is needed that is not caught by UNIVERSAL::callback ? No, afaik; it rather catches too much. If some package ought to have a `callback` method which it hasn't due to some fubar, `UNIVERSAL::callback` kicks in - long faces, head-scratching. But! if someone writes a method/function for package UNIVERSAL, they should know what they are doing, and my bets are that you do. perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'	[reply] [d/l] [select]
Re^4: Rosetta Dispatch Table by LanX (Saint) on Nov 26, 2017 at 18:54 UTC
Checking ->can is cleaner than adding a fallback method to UNIVERSAL. Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Wikisyntax for the Monastery}	[reply]