From: Richard Lee <[EMAIL PROTECTED]>
> http://www.stonehenge.com/merlyn/UnixReview/col08.html
>
> From above article, I am not fully understanding what's going on on
> below code.
>
> 1)is there any difference in $next = $non_blank(<STDIN>) and
> $next=$non_blank( sub{ <STDIN> }) in terms of funcaitonality?
Sure. (except that there should have been &non_blank, not $non_blank.
Or even better just non_blank()) In the first case the non_blank()
subroutine obtains as its parameters all the lines that can be read
from STDIN, while in the second case it obtains just one parameter. A
reference to a subroutine that reads one line from STDIN whenever
it's called.
If we name the subroutine the code would look like this:
sub read_from_stdin {
return <STDIN>;
}
...
$next = non_blank(\&read_from_stdin);
that is again the non_blank() would receive a reference to a
subroutine that reads one line from STDIN whenever called.
(actually this is not entirely true, the behaviour of the subroutine
in both cases depends on the context. In scalar context it reads just
one line, in list context it reads all remaining lines.)
> I am not fully understanding the difference in anonymous sub vs just
> having regular <STDIN> in there
>
> 2)in non_blank sub, my *guess is &{ $scanner }() is trying to
> dereference the anonymous sub routine... is () necessary there?
We need to dereference and thus call the subroutine, but you are
right that the () is not necessary there. I like this syntax better
though:
$scanner->()
but it means the same.
Jenda
===== [EMAIL PROTECTED] === http://Jenda.Krynicky.cz =====
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