Scalar::Util is core since 5.7.3. It features looks_like_number you can use to test whether anything has the format Perl uses for numbers.
Update: link fixed.
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[d/l] |
looks_like_number you can use to test whether anything has the format Perl uses for numbers
More specifically, if looks_like_number($x) returns false then perl should issue the "isn't numeric" warning for $x, but if looks_like_number($x) returns true then there should be no "isn't numeric" warning for $x.
This correlation doesn't hold for recent blead releases (including the current 5.21.8) wrt some 'inf' strings, and perhaps some 'nan' strings too.
But it should now be restored for 5.21.9.
That this correlation ought to exist might be no more than *my* opinion, though it seems obvious to me (and matches past behaviour afaik).
If someone has an example of it not holding in perl-5.20.x, I'd be interested to learn of it.
Cheers,
Rob
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{
local $SIG{__WARN__} = sub { print "Bad line: '$_'"; return; };
for( qw[ 1 2 3 d 5 f 6 ] ) {
print $_ * 2;
}
};;
2
4
6
Bad line: 'd'
0
10
Bad line: 'f'
0
12
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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[d/l] |
Maybe I misunderstand the question but, once you split your line into an array, you can test fields 6, 7 and 8 by doing something like this
use Scalar::Util (); # as advised by [choroba]
my ($line, @arr);
open my $fh, "<$ARGV[0]"
or die "failed to open file $ARGV[0] for reading: $!\n";
my @check_fields = (6, 7, 8);
my $line_counter = 0;
LINE:
while ($line = <$fh>) {
$line_counter++;
### skip line if any of fields 6-8 are not numeric
@arr = split /\s+/, $line;
foreach my $i ( @check_fields ) {
if ( ! Scalar::Util::looks_like_number($arr[$i - 1]) ) {
# bad;this checks only for positive integers
# (thanks Not_a_Number)
# if ($arr[$i - 1] !~ /^\d+$/) {
print STDERR "line num $line_counter: " .
"1st problem field $arr[$i - 1]: " .
"field num $i: " .
"$line\n";
next LINE;
}
}
### the rest of your code
}
This is just to show general approach. Code that does splitting and checking needs to be be extracted into a separate subroutine.
With respect to "millions of lines" context of the question, not sure how efficient or inefficient this code is. Caching of test results could be useful, but then caching can take a lot of memory and backfire.
Update: took into account Not_a_Number's comment. Added comment on "millions of lines" issue.
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[d/l] |
Scalars -7, 4.55, and 10e6 are all numeric. Your regex /^\d+$/ tests only for positive integers.
Update: Minor tpyo
Update 2: hotpelmen has now completely altered the content of her/his original post, without indicating that (s)he has made any changes (note to hotpelmen: this is considered Bad Form on PM).
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[d/l]
[select] |
Yeah, you caught me in the middle of my updates. I saved a few times before adding update statement. No preview for updates, that's a problem. Sorry for distress.
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[d/l] |
Isn't this a good example why one should use perl's taint mode?That will (gently) force you to check *all* data that comes from an outside and not fully trusted source. Regexp::Common may help you to check for real or integer numbers.
CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics
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