perl 4.0 patch 14: patch #11, continued

See patch #11.

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/exceptions.pl b/lib/exceptions.pl
new file mode 100644
index 0000000000..02c4498d32
--- /dev/null
+++ b/lib/exceptions.pl
@@ -0,0 +1,54 @@
+# exceptions.pl
+# tchrist@convex.com
+# 
+# Here's a little code I use for exception handling.  It's really just
+# glorfied eval/die.  The way to use use it is when you might otherwise
+# exit, use &throw to raise an exception.  The first enclosing &catch
+# handler looks at the exception and decides whether it can catch this kind
+# (catch takes a list of regexps to catch), and if so, it returns the one it
+# caught.  If it *can't* catch it, then it will reraise the exception
+# for someone else to possibly see, or to die otherwise.
+# 
+# I use oddly named variables in order to make darn sure I don't conflict 
+# with my caller.  I also hide in my own package, and eval the code in his.
+# 
+# The EXCEPTION: prefix is so you can tell whether it's a user-raised
+# exception or a perl-raised one (eval error).
+# 
+# --tom
+#
+# examples:
+#	if (&catch('/$user_input/', 'regexp', 'syntax error') {
+#		warn "oops try again";
+#		redo;
+#	}
+#
+#	if ($error = &catch('&subroutine()')) { # catches anything
+#
+#	&throw('bad input') if /^$/;
+
+sub catch {
+    package exception;
+    local($__code__, @__exceptions__) = @_;
+    local($__package__) = caller;
+    local($__exception__);
+
+    eval "package $__package__; $__code__";
+    if ($__exception__ = &'thrown) {
+	for (@__exceptions__) {
+	    return $__exception__ if /$__exception__/;
+	} 
+	&'throw($__exception__);
+    } 
+} 
+
+sub throw {
+    local($exception) = @_;
+    die "EXCEPTION: $exception\n";
+} 
+
+sub thrown {
+    $@ =~ /^(EXCEPTION: )+(.+)/ && $2;
+} 
+
+1;