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99b89507 LW |
1 | # exceptions.pl |
2 | # tchrist@convex.com | |
a6d71656 GS |
3 | # |
4 | # This library is no longer being maintained, and is included for backward | |
5 | # compatibility with Perl 4 programs which may require it. | |
25209816 S |
6 | # This legacy library is deprecated and will be removed in a future |
7 | # release of perl. | |
a6d71656 GS |
8 | # |
9 | # In particular, this should not be used as an example of modern Perl | |
10 | # programming techniques. | |
25209816 | 11 | |
99b89507 LW |
12 | # Here's a little code I use for exception handling. It's really just |
13 | # glorfied eval/die. The way to use use it is when you might otherwise | |
14 | # exit, use &throw to raise an exception. The first enclosing &catch | |
15 | # handler looks at the exception and decides whether it can catch this kind | |
16 | # (catch takes a list of regexps to catch), and if so, it returns the one it | |
17 | # caught. If it *can't* catch it, then it will reraise the exception | |
18 | # for someone else to possibly see, or to die otherwise. | |
19 | # | |
20 | # I use oddly named variables in order to make darn sure I don't conflict | |
21 | # with my caller. I also hide in my own package, and eval the code in his. | |
22 | # | |
23 | # The EXCEPTION: prefix is so you can tell whether it's a user-raised | |
24 | # exception or a perl-raised one (eval error). | |
25 | # | |
26 | # --tom | |
27 | # | |
28 | # examples: | |
29 | # if (&catch('/$user_input/', 'regexp', 'syntax error') { | |
30 | # warn "oops try again"; | |
31 | # redo; | |
32 | # } | |
33 | # | |
34 | # if ($error = &catch('&subroutine()')) { # catches anything | |
35 | # | |
36 | # &throw('bad input') if /^$/; | |
37 | ||
38 | sub catch { | |
39 | package exception; | |
40 | local($__code__, @__exceptions__) = @_; | |
41 | local($__package__) = caller; | |
42 | local($__exception__); | |
43 | ||
44 | eval "package $__package__; $__code__"; | |
45 | if ($__exception__ = &'thrown) { | |
46 | for (@__exceptions__) { | |
47 | return $__exception__ if /$__exception__/; | |
48 | } | |
49 | &'throw($__exception__); | |
50 | } | |
51 | } | |
52 | ||
53 | sub throw { | |
54 | local($exception) = @_; | |
55 | die "EXCEPTION: $exception\n"; | |
56 | } | |
57 | ||
58 | sub thrown { | |
59 | $@ =~ /^(EXCEPTION: )+(.+)/ && $2; | |
60 | } | |
61 | ||
62 | 1; |