On Tue, Jan 27, 2004 at 05:04:03PM -0500, Tolkin, Steve wrote:
> # run using e.g. echo hello | perl this-file
>
> # Why doesn't perl produce a warning from the following. It is an
> # infinite loop. If I add a /g modifier to the m// it works fine.
>
> while (<>) {
> while (m/([a-z])/) { # warning infinite loop!!!
> print $1, "\n"
> }
> }
>
>
> ///
>
> In general it is hard to detect infinite loops, but in this case it is easy,
> because the pattern is a constant. I think this is a very common
> special case, and is worth detecting.
The pattern in the below code is also constant, but there is no infinite
loop:
while (<>) {
while (m/([a-z])/) {
print $1, "\n";
$_ = substr($_, 1);
}
}
As you say, it is hard to detect infinite loops. :)
Ronald
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