Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??

I have run across a situation where I need a Switch statement.

That need is of your own creation. There is no situation where the lack of a switch statement will prohibit the project from moving forward with efficiency and clarity. Perl5 was a dozen years old before it got a switch statement (called given/when), and the addition of that syntax didn't make any application of the Perl language that previously would have been impossible suddenly become possible. In fact, Perl's switch statement has been mostly repealed (or flagged as experimental) in modern releases of Perl.

given/when is a programmer convenience, not a language necessity. Use if/elsif/else, or a hash table filled with code refs, or if you're concerned about efficiency, use an array-table filled with coderefs, and assign constants that refer to the elements. Even if you're trying to make your decision based on pattern matching, that's not difficult:

use constant { RE_TRIGGER => 0, CODEREF => 1, }; my @dispatch = ( [ qr/this/, \&do_that ], [ qr/those, \&do_these ], ); DISPATCH: for ( @dispatch ) { $string =~ $_->[RE_TRIGGER] && do{ $_->[CODEREF]->(); last DISPATCH; }; }

In this example I'm populating an array with a series of patterns and actions to take if a given pattern matches. I have control over which match is tested first, because I'm using an array for the dispatch table. And I have control over whether to continue on to the next test, or abort upon success by the use (or omission) of last DISPATCH. I can even add a default by including a regex test as the last element in @dispatch that will always succeed.

Is it more clear than a series of if/elsif/else statements? I guess that depends on how many tests are being conducted. If it's just a small few, chained if/elsif's are probably clearer. If there are a lot of options, a table works well.

If you make the first element a subref instead of a regexp object, you have even more control, and a more generalized solution.


Dave


In reply to Re: Given When Syntax by davido
in thread Given When Syntax by Deep_Plaid

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



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others wandering the Monastery: (2)
As of 2024-04-20 04:24 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found