Re: Hash return value
Yeah that's what I started to suspect after I posted. mkhash() should be
saved to a variable name and that variable used in the while each loop.
At 01:18 PM 3/18/2006 +1100, Sisyphus wrote:
>That's not what I find.
>The following script (suggested by Chris) simply prints "All done" for me.
>
my($key, $value);
%temp = mkhash();
while (($key, $value)= each( %temp ))
>my($key, $value);
>while (($key, $value)= each( %{mkhash()} ))
>{
>print("$key = $value\n");
>}
>
>print "All done\n";
>
>sub mkhash
>{
> my %hash=('one'=>1, 'two'=>2, 'three'=>3);
> return %hash;
>}
>
>__END__
three = 3
one = 1
two = 2
All done
--
REMEMBER THE WORLD TRADE CENTER ---=< WTC 911 >=--
"...ne cede malis"
0100
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Re: Hash return value
- Original Message -
From: "Eric Amick"
.
.
> You can return a reference to a
> hash instead and then dereference it in the caller:
>
> while (($key, $value)= each( %{ mkhash() }))
> {
> print("$key = $value\n");
> }
>
> sub mkhash
> {
> my %hash=('one'=>1, 'two'=>2, 'three'=>3);
> return \%hash;
> }
That's not what I find.
The following script (suggested by Chris) simply prints "All done" for me.
use warnings;
my($key, $value);
while (($key, $value)= each( %{mkhash()} ))
{
print("$key = $value\n");
}
print "All done\n";
sub mkhash
{
my %hash=('one'=>1, 'two'=>2, 'three'=>3);
return %hash;
}
__END__
Run it under strictures and I get the fatal error:
Can't use string ("3/8") as a HASH ref while "strict refs" in use.
If I change mkhash() so that it returns a hashref (as you've suggested
above), I just get (ad infinitum):
three = 3
three = 3
three = 3
three = 3
three = 3
three = 3
three = 3
three = 3
three = 3
three = 3
.
.
Looks to me that all you've succeeded in doing is find a way around the
safeguard that was put in place - and that neverending ouptut is pretty much
what I would expect to see when that safeguard has been breached. At each
iteration of the while loop, mkhash() gets re-run and each() gets a new
anonymous hash to deal with.
Cheers,
Rob
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Re: Hash return value
On Fri, 17 Mar 2006 12:05:07 -0800, you wrote:
># Using subroutine that returns a hash doesn't work
>while (($key, $value)= each( mkhash() ))
>{
>print("$key = $value\n");
>}
>
>sub mkhash
>{
> my %hash=('one'=>1, 'two'=>2, 'three'=>3);
> return %hash;
>}
The each() function expects its argument to start with %. As perlsub
explains, your function actually returns a list, not a hash; arrays and
hashes are "flattened" when returned from a function, just as they're
flattened when passed to a function. You can return a reference to a
hash instead and then dereference it in the caller:
while (($key, $value)= each( %{ mkhash() }))
{
print("$key = $value\n");
}
sub mkhash
{
my %hash=('one'=>1, 'two'=>2, 'three'=>3);
return \%hash;
}
--
Eric Amick
Columbia, MD
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Re: Hash return value
At 04:40 PM 3/16/2006 -0700, Edwards, Mark (CXO) wrote:
>The each function requires a hash as an argument. I would think that a
>subroutine that returns a hash could be used as the argument, but it
>doesn't work. Why? Is my syntax wrong or is that just the way Larry
>made it?
U have to evaluate it in hash context. This should work.
while (($key, $value)= each( %{&mkhash()} )) {
print("$key = $value\n");
}
--
REMEMBER THE WORLD TRADE CENTER ---=< WTC 911 >=--
"...ne cede malis"
0100
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Re: Hash return value
- Original Message - From: "Edwards, Mark (CXO)" . . > # Using subroutine that returns a hash doesn't work > while (($key, $value)= each( mkhash() )) One problem with allowing that is that at each iteration of the while loop, mkhash() gets re-run, returning another anonymous hash. The each() function can deal with only one hash at a time - and yet it would be seeing a separate additional anonymous hash at each iteration of the while loop. (What would happen if mkhash() returned *different* hashes at each iteration.) I think it may also be that each() needs a *named* hash so that it "can keep track of where it's up to" so to speak . not sure about that. Cheers, Rob ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
Hash return value
The each function requires a hash as an argument. I would think that a
subroutine that returns a hash could be used as the argument, but it
doesn't work. Why? Is my syntax wrong or is that just the way Larry
made it?
use warnings;
use strict;
my ($key, $value, %hash) ;
# Using hash for function argument works
%hash=mkhash();
while (($key, $value)= each( %hash ))
{
print("$key = $value\n");
}
# Using subroutine that returns a hash doesn't work
while (($key, $value)= each( mkhash() ))
{
print("$key = $value\n");
}
sub mkhash
{
my %hash=('one'=>1, 'two'=>2, 'three'=>3);
return %hash;
}
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