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Re^2: Switch - "case" may clash with future reserved word

by erroneousBollock (Curate)
on Nov 29, 2007 at 01:46 UTC ( #653741=note: print w/ replies, xml ) Need Help??


in reply to Re: Switch - "case" may clash with future reserved word
in thread Switch - "case" may clash with future reserved word

I wouldn't say Switch.pm is buggy (update: in this specific case).

It is a very simplistic source-filter, which gives you plenty of warning in its documentation on the risks and limits of its use.

A "dispatch table" (as the hash of subs is usually called) is indeed a very useful construct, but sometimes a real switch/case-like construct is better.

For example, if your algorithm calls for falling through from one case to another, it's hard to achieve that cleanly with a dispatch table (without additional external machinery).

As mentioned above, Perl 5.10 (and 6) will introduce the given/when construct, which works like switch/case but is more powerful. The switch/case construct in most languages allows only integer or scalar values in case expressions, but given/when will allow many more possibilities (by using the "smart match" operator). Example:

given $data { when /^\d+$/ { return %var{""} = $_ } when 'previous' { return %var{""} // fail NoData } when %var { return %var{""} = %var{$_} } default { die Err::BadData : msg=>"Don't understand $_" } }
I know I'll be using it with abandon as soon as 5.10 comes out :-)

-David


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