On Mon, Jan 17, 2011 at 12:52 AM, Shmuel Fomberg <[email protected]> wrote:
> Hi All.
>
Hey!
> Why would anyone read a file in a for loop?
>
If you read using a while(), you're reading one line at a time, because
while() has to run the code in the condition and evaluate the result as a
boolean. If you're reading using foreach(), you're forcing the condition to
be evaluated to a list that you will then iterate over.
Basically meaning that:
foreach my $line (<$fh>) { ... }
# is equal to:
my @lines = <$fh>;
foreach my $line (@lines) { ... }
---
And that:
while ( my $line = <$fh> ) { ... }
# is equal to:
while (1) {
eof($fh) and last;
my $line = <$fh>; # get single line
...
}
---
I think what chromatic meant was that you need to *know* what the difference
is. I don't personally understand *why* someone would prefer foreach() over
while(), but I know what it really means: pre-evaluation of all accounts,
which is heavier on the memory.
Hope that helps,
Sawyer.
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