Re^2: Hash keys affect sorting

I'm a baby monk only... ;)

Have to admit I have never seen @_ used for anything else than for function arguments, and I don't exactly understand push @data, [@_]; Using @_ seems nice and intuitive, applying it to my example gives me:

use strict;
my $output = <<EOD;
4865FA9B   0702 P H rmt0           TAPE OPERATION ERROR
DE9A52D1   0704 I S rmt0           DEVICE DUMP RETRIEVED
4865FA9B   0701 P H rmt2           TAPE OPERATION ERROR
F3E9B3E2   0620 I O SYSJ2          UNABLE TO ALLOCATE SPACE IN FILE SY
+STEM
DCB47997   0511 T H hdisk4         DISK OPERATION ERROR
EOD

my (@data, %identifier);
for my $line (split /\n/,$output) {
    @_ = split /\s+/, $line, 6;
    push @data, [@_];
    $identifier{$_[0]} = $data[-1]; # Index for first field
}

# Sort on multiple fields, in this case 4th (class) and 2nd (time)...
print "\@data:\n";
for my $rec (reverse sort {$a->[3] cmp $b->[3] || $a->[1] <=> $b->[1]}
+ @data) {
   print "Error ID: $rec->[0]   Time: $rec->[1]\n";
}
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Also, if i understand you right, %identifier contains a hash of array references which I can use to access @data elements e.g.

print "key $_ value: $identifier{$_}->[0]\n" for (keys %identifier);

Thanks for the help!

Niel

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Re^3: Hash keys affect sorting by shmem (Chancellor) on Jul 07, 2006 at 23:03 UTC
`$_` is to scalar what `@_` is to array and `%_` is to hash, although `%_` is seldom seen in the wild. `push @data, [@_]` means: `$_` was split into `@_`; if they said `push @data, @_` the array `@_` would append it's elements to `@data`. To append `@_` as one unit to `@data` it must be given boundaries `[ ]`; this construct creates an array reference. This reference (a scalar) is stored in `@data`, holding the elements of `@_` which are copied into `[ ]` at the moment of creation of `[ ]`. See perlreftut. Think of `[@_]` as "scalarifying" `@_` into an (anonymous) array reference; an array can only hold scalars (single values, which references happen to be). Wow. What noise ;-) hoping not to have confused you further, --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l] [select]

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Re^3: Hash keys affect sorting
by shmem (Chancellor) on Jul 07, 2006 at 23:03 UTC

$_

@_

%_

push @data, [@_] means: $_ was split into @_; if they said push @data, @_ the array @_ would append it's elements to @data. To append @_ as one unit to @data it must be given boundaries [ ]; this construct creates an array reference. This reference (a scalar) is stored in @data, holding the elements of @_ which are copied into [ ] at the moment of creation of [ ]. See perlreftut. Think of [@_] as "scalarifying" @_ into an (anonymous) array reference; an array can only hold scalars (single values, which references happen to be).

Wow. What noise ;-)

hoping not to have confused you further,
--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

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