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# exceptions.pl |
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# tchrist@convex.com |
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# |
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# This library is no longer being maintained, and is included for backward |
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# compatibility with Perl 4 programs which may require it. |
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# |
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# In particular, this should not be used as an example of modern Perl |
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# programming techniques. |
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# |
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# |
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# Here's a little code I use for exception handling. It's really just |
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# glorfied eval/die. The way to use use it is when you might otherwise |
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# exit, use &throw to raise an exception. The first enclosing &catch |
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# handler looks at the exception and decides whether it can catch this kind |
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# (catch takes a list of regexps to catch), and if so, it returns the one it |
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# caught. If it *can't* catch it, then it will reraise the exception |
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# for someone else to possibly see, or to die otherwise. |
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# |
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# I use oddly named variables in order to make darn sure I don't conflict |
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# with my caller. I also hide in my own package, and eval the code in his. |
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# |
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# The EXCEPTION: prefix is so you can tell whether it's a user-raised |
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# exception or a perl-raised one (eval error). |
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# |
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# --tom |
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# |
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# examples: |
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# if (&catch('/$user_input/', 'regexp', 'syntax error') { |
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# warn "oops try again"; |
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# redo; |
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# } |
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# |
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# if ($error = &catch('&subroutine()')) { # catches anything |
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# |
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# &throw('bad input') if /^$/; |
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sub catch { |
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package exception; |
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local($__code__, @__exceptions__) = @_; |
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local($__package__) = caller; |
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local($__exception__); |
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eval "package $__package__; $__code__"; |
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if ($__exception__ = &'thrown) { |
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for (@__exceptions__) { |
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return $__exception__ if /$__exception__/; |
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} |
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&'throw($__exception__); |
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} |
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} |
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sub throw { |
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local($exception) = @_; |
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die "EXCEPTION: $exception\n"; |
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} |
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sub thrown { |
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$@ =~ /^(EXCEPTION: )+(.+)/ && $2; |
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} |
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1; |
