Re: References/unitialized variable error message
In article <[EMAIL PROTECTED]> wrote "Geoffrey F. Green"
<[EMAIL PROTECTED]>:
> #!/usr/bin/perl -w
>
> my %table = (
> "key1" =>
> {search=> "alpha",
> shortname=> "beta",
> },
> "key2" =>
> {search => "gamma",
> shortname=> "delta",
> },
> "key3" =>
> {search=> "epsilon",
> shortname=> "whatever",
> },
>);
I'd like to give another hint:
I find it dangerous, to repeat in every line search and shortname.
The chance of mistyping is really big.
Even if you use Copy+Paste (what's never a good solution)
you get the trouble when changing later.
Again, I would be too lazy - even for writing and for reading :-)
Here's one possibility:
my %table = map {
my ($key, $search, $short) = split / /, $_;
($key => { search=> $search,
shortname => $shortname
}
)
} split /\n/, <<'TABLE';
key1 alpha beta
key2 gamma delta
key3 epsilon whatever
TABLE
That of course only goes strait when the keys don't have white spaces.
And again, it only makes sense when you will use more than 3 keys a day.
Greetings,
Andrea
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Re: References/unitialized variable error message
On 2/16/02 7:15 PM, "Briac Pilpré" <[EMAIL PROTECTED]> wrote: > To iterate over a hash, you want to use the keys() function. I once knew that, but I haven't used perl enough so I forgot. I gues that's why they call this list "Beginners." Thanks a lot - geoff -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: References/unitialized variable error message
On Sat, Feb 16, 2002 at 07:07:28PM -0500, Geoffrey F. Green wrote:
> my %table = (
> "key1" =>
> {search=> "alpha",
> shortname=> "beta",
> },
> "key2" =>
> {search => "gamma",
> shortname=> "delta",
> },
> "key3" =>
> {search=> "epsilon",
> shortname=> "whatever",
> },
> );
>
> foreach my $keys (%table) {
You say $keys here, and treat $keys as a key, but when you iterate over
%table you're iterating over the list ('key1', $hashref1, 'key2', $hashref2,
'key3', $hashref3), i.e. both the keys -and- the values. You should be
using keys(%table).
foreach my $keys (keys %table) { ... }
Also, I'd suggest naming it $key, not $keys; you're accessing one key at a
time, not multiple keys.
> print $table{$keys}->{search},"\n";
> print $table{$keys}->{shortname},"\n";
> };
> Camel's description of the error, and undefined variables, didn't clarify
> matters for me, and unless I missed something fundamental, the FAQ didn't
> have an answer to this conundrum.
I'm not sure why you didn't understand the description, possibly because you
didn't expect the error from what you were using.
The problem occurred because you were trying to access
$table{$hashref1}->{search}. There was no such key, so you got undef.
> I also can't remember, off the top of my head, the sixth letter of the
> Greek alphabet, but that's not important right now.
zeta
> 2. I also don't understand the extra newline I get between each pass of the
> foreach loop. With warnings disabled, the output is as follows:
Just because one of the values in your print statement is undefined doesn't
mean the entire print statement is ignored.
You have:
print $table{$keys}->{search}, "\n";
If $table{$keys}->{search} is undefined, it's stringified to "" and a
warning is issued. So, in effect, you have:
print "", "\n";
Which prints just a newline, thus the "extra" whitespace.
Michael
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Re: References/unitialized variable error message
On Sun, 17 Feb 2002 at 00:07 GMT, Geoffrey F. Green wrote:
> Hi. Newbie to perl here. I've got two problems (well, two perl-related
> problems), relating to the same program.
To iterate over a hash, you want to use the keys() function.
foreach my $keys ( keys %table) {
print $table{$keys}->{search},"\n";
print $table{$keys}->{shortname},"\n";
}
Otherwise, perl iterates alternatively over the keys and the values of
the hash, which causes the extra newlines and the warnings.
--
briac
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References/unitialized variable error message
Hi. Newbie to perl here. I've got two problems (well, two perl-related
problems), relating to the same program.
1. I'm putting together some test programs to try to get down the syntax for
references, etc., but I'm coming across a weird situation I can't figure
out. I'm setting up a hash of hashes. For some reason, I'm being told that
a particular variable that I want printed is uninitialized -- but then perl
goes ahead and prints the variable.
Here's the test program, named "referencespractice.pl":
#!/usr/bin/perl -w
my %table = (
"key1" =>
{search=> "alpha",
shortname=> "beta",
},
"key2" =>
{search => "gamma",
shortname=> "delta",
},
"key3" =>
{search=> "epsilon",
shortname=> "whatever",
},
);
foreach my $keys (%table) {
print $table{$keys}->{search},"\n";
print $table{$keys}->{shortname},"\n";
};
I expect this output:
alpha
beta
gamma
delta
epsilon
whatever
Instead, I get this:
alpha
beta
Use of uninitialized value in print at ./referencespractice.pl line 20.
Use of uninitialized value in print at ./referencespractice.pl line 21.
gamma
delta
Use of uninitialized value in print at ./referencespractice.pl line 20.
Use of uninitialized value in print at ./referencespractice.pl line 21.
epsilon
whatever
Use of uninitialized value in print at ./referencespractice.pl line 20.
Use of uninitialized value in print at ./referencespractice.pl line 21.
(Needless to say, the errors occur within the two lines in the foreach
loop.)
Camel's description of the error, and undefined variables, didn't clarify
matters for me, and unless I missed something fundamental, the FAQ didn't
have an answer to this conundrum. I also can't remember, off the top of my
head, the sixth letter of the Greek alphabet, but that's not important right
now.
2. I also don't understand the extra newline I get between each pass of the
foreach loop. With warnings disabled, the output is as follows:
alpha
beta
gamma
delta
epsilon
whatever
Why are there extra newlines?
Thanks in advance.
- geoff
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