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Is there a equiv. for SELECT CASE or SWITCH

Posted on 1997-12-22
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Last Modified: 2008-03-10
I'm searching for the perl equivalent of the VB command SELECT CASE or the identical SWITCH command in C.
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Question by:Kobe_Lenjou
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10 Comments
 
LVL 2

Expert Comment

by:haystor
ID: 1209380
There is no direct equivalent, but something close can be constructed using if-elsif-else...
for instance:

if ($a eq "a") {
   print "a\n";
} elsif ($b eq "b") {
   print "b\n";
} else {
   print "it was neither a nor b\n";
}

The equivalent of fall throughs are best constructed using multiple if's altough the conditionals can become complicated.
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LVL 51

Expert Comment

by:ahoffmann
ID: 1209381
I prefer:

SWITCH: {
    $_=$a;
    /^a$/ && do { ..; last SWITCH; };
    /^b$/ && do { ..; last SWITCH; };
    # default follows here
}
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LVL 84

Expert Comment

by:ozo
ID: 1209382
or:

for( $a ){
  /^a$/ && do { ..; last }
  /^b$/ && do { ..; last }
  # default follows here
}

or even:

%switch=(
'a'=>sub{print "a\n"},
'b'=>sub{print "b\n"},
);
&{$switch{$a}||sub{print "it was neither a nor b\n"}}

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LVL 84

Expert Comment

by:ozo
ID: 1209383
BTW, Kobe_Lenjou, got a server error on your question qid=8630031117,
and couldn't read the last comment you added there.
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Expert Comment

by:mgjv
ID: 1209384
to find more possibilities to do the same thing, simply read the perlsyn documentation that comes with perl.

perldoc perlsyn

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Author Comment

by:Kobe_Lenjou
ID: 1209385
I like the answer of ozo and I want to give you the credit for this one.

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LVL 8

Author Comment

by:Kobe_Lenjou
ID: 1209386
Note to ozo,i get the server erorr myself :(
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LVL 84

Expert Comment

by:ozo
ID: 1209387
Which answer?  As mgjv says, most of these suggestions, and several more, are given in perlsyn.
(The &{$switch} method is not given in perlsyn, but it can be inferred from perlref.)

If qid=8630031117 has gotten lost, you may want to email linda@experts-exchange.com
or post a question to the customer service area to recover your points
so you can post that question again.
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LVL 1

Expert Comment

by:hank1
ID: 1209388
<<__comments__;

Here's a switchy thing I use.  By-the-way I understand switch
is on its way.

__comments__


$switchee = 'b';
SWITCH: {
  if($switchee eq 'a'){
    print "Is a.\n";
    last SWITCH;
  }
  if($switchee eq 'b'){
    print "Is b.\n";
    last SWITCH;
  }
  if($switchee eq 'c'){
    print "Is c.\n";
    last SWITCH;
  }
  if($switchee eq 'd'){
    print "Is d.\n";
    last SWITCH;
  }
  print "Is not a, b, c or d.\n";
  last SWITCH;
}



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LVL 84

Accepted Solution

by:
ozo earned 50 total points
ID: 1209389
for( $a ){
  /^a$/ && do { print "a\n"; last }
  /^b$/ && do { print "b\n"; last }
  # default follows here
  print "it was neither a nor b\n";
}
#or
%switch=(
                        'a'=>sub{print "a\n"},
                        'b'=>sub{print "b\n"},
);
&{$switch{$a}||sub{print "it was neither a nor b\n"}}  
#or see perlsyn or perlfaq7
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