On Jul 31, 2014, at 12:02 PM, ESChamp wrote:
> John W. Krahn wrote on 7/31/2014 3:11 AM:
>> Peter Holsberg wrote:
>>> I think I've isolated the section that is not doing what I want.
>>>
>>> open (FHIN, "$recapfile") or die $!;
>>
>> That would be better as:
>>
>> open my $FHIN, '<', $recapfile or die "Cannot open '$recapfile' because:
>> $!";
>
> Thanks, John. As this is a beginners list and I'm an elderly beginner
> who is an occasional perl user, what makes that better?
It is better because 1) it uses the three-argument form of open instead of the
two-argument version (the two-argument version has known risks), 2) it doesn't
put the variable containing the file name in superfluous double-quotes, 3) it
adds the file name to the error message, and 4) it uses a local lexical
variable instead of a global bareword package variable.
>>> my $indexb; ## for the recapfile array
>>> my $ofile;
>>
>> You never use this variable, it should be:
>>
>> my @ofile;
>
> Could you kindly explain that?
You are declaring a scalar variable $ofile, but in your code below you use the
array variable @ofile. These are not the same thing. If you put 'use strict;'
at the beginning of your program, Perl will inform you that you have not
declared @ofile.
>>> # Create new array containing all the lines of recapfile up to
>>> # the string RESULTS OF BOARD 1
>>>
>>> XYZZY:
>>> while (<FHIN>)
>>> {
>>> last XYZZY if / RESULTS OF BOARD 1/;
>>> chomp;
>>> $ofile[$indexb++] .= $_;
>>
>> That would be better as:
>>
>> push @ofile, $_;
>>> }
>>> close FHIN;
>
> Exactly what lines would yours replace? Why would that be better?
push @file, $_;
replaces
$ofile[$indexb++] .= $_;
This is better because 1) it is simpler and therefore less likely to contain an
error, 2) uses a Perl built-in function instead of hand-crafted code, 3)
doesn't use an additional variable ($indexb), 4) doesn't use the unnecessary
concatenation operator '.=' where a simple assignment '=' would do.
x .= y
is equivalent to
x = x . y
While this works in your case because the elements of @ofile are all undefined,
and concatenating a string to an undefined value results in a simple
assignment, it is a superfluous operation.
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