Re: Unpack Many Fields

If you only need 34 of 170 fields, you can use x[nnn] to skip the bytes between the fields you want. That should reduce the unweildy length of your template considerably.

And if the template is still uncomfortably long:

my $fmt = join '', qw[
    x[10] a5
    x[22] a10
    x[4]  a3 a2
    ...
];
[download]

You can even turn that into an opportunity to document:

my $fmt = join '', grep !m[^#], qw[
    x[10] a5     #code
    x[22] a10    #thingummy
    x[4]  a3 a2  #doodah&whatsit
    ...
];
[download]

As for the naming of the fields, rather than using strings of "FIELDnn" in a hash, why not use an array?

Eg.

my $fmt = "x[10]a5x[22]a10x[4]a3a2...";
my %hash;
while( <$fh> ) {
    my( $code, @fields ) = unpack $fmt, $line;
    $hash->{$code} = \@fields;
}
...
for my $code ( keys %hash ) {
    print $hash->{ $code }[ $_ ] for 0 .. 33;
}
[download]

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"I'd rather go naked than blow up my ass"

Comment on Re: Unpack Many Fields Select or Download Code

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Re^2: Unpack Many Fields by ikegami (Patriarch) on Feb 16, 2010 at 01:53 UTC
Using `#` in `qw` causes a warning. The following removes warnings and allows spaces to be used in the comment: `my $fmt = q[ x[10] a5 # code x[22] a10 # thingummy x[4] a3 a2 # doodah & whatsit ]; $fmt =~ s/#.//g;` [download] But `pack` allows for comments in patterns, so one doesn't even need that last line. Update*: Originally, the `/g` was missing, which led me to discover that one doesn't need to remove the comments.	[reply] [d/l] [select]
Re^3: Unpack Many Fields by shoness (Friar) on Feb 16, 2010 at 02:23 UTC
I think it has to be something like `$fmt =~ s/(?:#.*)\|\n\|\s//g;` [download] Thanks to both of you! My code is already looking much better. Cheers!	[reply] [d/l]
Re^4: Unpack Many Fields by ikegami (Patriarch) on Feb 16, 2010 at 02:47 UTC
Not at all. For starters, `s/(?:#.)\|\n\|\s//g` [download] is the same as `s/#.\|\s//g` [download] Secondly, spaces are allowed in the pattern, so your change is unwarranted. Finally, comments are allowed in the pattern, so you don't need the substitution at all.	[reply] [d/l] [select]
Re^5: Unpack Many Fields by shoness (Friar) on Feb 16, 2010 at 02:54 UTC
Re^3: Unpack Many Fields by BrowserUk (Patriarch) on Feb 16, 2010 at 03:01 UTC
Whaddayaknow! That definitely deserves a mench in perlfunc. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "I'd rather go naked than blow up my ass"	[reply]
Re^4: Unpack Many Fields by ikegami (Patriarch) on Feb 16, 2010 at 05:09 UTC
It does. The first sentence of the following is present since at least 5.6.0: A comment in a TEMPLATE starts with `#` and goes to the end of line. White space may be used to separate pack codes from each other, but modifiers and a repeat count must follow immediately. It would be nice if WS and `#` were mentioned in the table at the top, though.	[reply] [d/l] [select]
Re^5: Unpack Many Fields by BrowserUk (Patriarch) on Feb 16, 2010 at 05:48 UTC


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