Re: Test if string is a number?
Lyle Kopnicky wrote: Thanks folks. I think I'll go with looks_like_number from Scalar::Util. I like to use library routines where possible. I don't know how I overlooked that, since I poked through Scalar::Util earlier. It just seems bizarre to me that something like that isn't a builtin. I mean, you can't even tell strings from numbers? I'm used to working in strongly typed languages. If you always are careful to put things away that you know what they are, it's not necessary. IE: before you store some external piece of data - determine exactly what it is and format it in a manner that you don't have bother worrying about later. So when something first arrives in a vrbl, that's the time to get it into a strict format so you needn't worry about it later. -- ,-/- __ _ _ $Bill LuebkertMailto:[EMAIL PROTECTED] (_/ / )// // DBE CollectiblesMailto:[EMAIL PROTECTED] / ) /-- o // // Castle of Medieval Myth Magic http://www.todbe.com/ -/-' /___/__/_/_http://dbecoll.tripod.com/ (My Perl/Lakers stuff) ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
Re: Test if string is a number?
Wow there's been a lot of heavy duty code proposed to do something so simple. The answer is in how Perl converts between the two. print is a number if $var eq $var + 0; print not a number if $var ne $var + 0; Say $var is bob. In the first case we see if bob is string equal to bob + 0 or is bob eq 0. Obviously not. Say $var is 5. In the second case we see if 5 is not string equal to 5 + 0 or is 5 ne 5. In this setup we're forcing the variable into numeric context and then back into string context. How the variable survives that procedure depends on whether it is number like or not number like. At 08:31 PM 6/29/05 -0700, Lyle Kopnicky wrote: Thanks folks. I think I'll go with looks_like_number from Scalar::Util. I like to use library routines where possible. I don't know how I overlooked that, since I poked through Scalar::Util earlier. It just seems bizarre to me that something like that isn't a builtin. I mean, you can't even tell strings from numbers? I'm used to working in strongly typed languages. -- REMEMBER THE WORLD TRADE CENTER ---= WTC 911 =-- ...ne cede males 0100 ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
RE: Test if string is a number?
Wow there's been a lot of heavy duty code proposed to do something so simple. The answer is in how Perl converts between the two. print is a number if $var eq $var + 0; print not a number if $var ne $var + 0; That fails on 1e7. ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
RE: Test if string is a number?
Title: Re: Test if string is a number? Chris Wagner wrote, on Thu 6/30/2005 08:48 : Wow there's been a lot of heavy duty code proposed to do something so: simple. The answer is in how Perl converts between the two.:: print "is a number" if $var eq $var + 0;: print "not a number" if $var ne $var + 0; Except if $var is, say, '0.00'. Then $var + 0 is '0', and won't eq $var. Joe == Joseph P. Discenza, Sr. Programmer/Analyst mailto:[EMAIL PROTECTED] Carleton Inc. http://www.carletoninc.com 574.243.6040 ext. 300 fax: 574.243.6060Providing Financial Solutions and Compliance for over 30 Years ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
Re: Test if string is a number?
Chris Wagner wrote: Wow there's been a lot of heavy duty code proposed to do something so simple. The answer is in how Perl converts between the two. print is a number if $var eq $var + 0; print not a number if $var ne $var + 0; Say $var is bob. In the first case we see if bob is string equal to bob + 0 or is bob eq 0. Obviously not. Say $var is 5. In the second case we see if 5 is not string equal to 5 + 0 or is 5 ne 5. In this setup we're forcing the variable into numeric context and then back into string context. How the variable survives that procedure depends on whether it is number like or not number like. Some of us use strict and warnings. What happens with this ? : use strict; use warnings; my $var = undef; print is a number if $var eq $var + 0; print not a number if $var ne $var + 0; and my $var = 'bob'; print is a number if $var eq $var + 0;# will give a warning if $var not a number -- ,-/- __ _ _ $Bill LuebkertMailto:[EMAIL PROTECTED] (_/ / )// // DBE CollectiblesMailto:[EMAIL PROTECTED] / ) /-- o // // Castle of Medieval Myth Magic http://www.todbe.com/ -/-' /___/__/_/_http://dbecoll.tripod.com/ (My Perl/Lakers stuff) ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
Re: Test if string is a number?
Title: Re: Test if string is a number? How about regexp? /^\-?(\d+\.?\d*|\.\d+)$/ - Original Message - From: Joe Discenza To: Chris Wagner ; perl-win32-users Sent: Thursday, June 30, 2005 4:48 PM Subject: RE: Test if string is a number? Chris Wagner wrote, on Thu 6/30/2005 08:48 : Wow there's been a lot of heavy duty code proposed to do something so: simple. The answer is in how Perl converts between the two.:: print "is a number" if $var eq $var + 0;: print "not a number" if $var ne $var + 0; Except if $var is, say, '0.00'. Then $var + 0 is '0', and won't eq $var. Joe == Joseph P. Discenza, Sr. Programmer/Analyst mailto:[EMAIL PROTECTED] Carleton Inc. http://www.carletoninc.com 574.243.6040 ext. 300 fax: 574.243.6060Providing Financial Solutions and Compliance for over 30 Years ___Perl-Win32-Users mailing listPerl-Win32-Users@listserv.ActiveState.comTo unsubscribe: http://listserv.ActiveState.com/mailman/mysubs ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
RE: Test if string is a number?
For a long time I'm using the function below to test for a number, being
quite satisfied with it ...
# (nmb) number
# Returns decimal value of the contents if argument
# is a number (integer if octal or hexadecimal),
# otherwise returns empty string ('')
sub number($) {
local $_ = shift; s/^\s*(.*)\s*$/$1/;
return '' unless
/^[+-]?(?:\d+\.?\d*|\.\d+)(?:[eE][+-]?\d+)?$|^[+-]?0x[0-9a-fA-F]+$/;
s/\+//; my $sign = s/^-// ? '-' : '';
/^0[0-7]+$|^0x[0-9a-fA-F]+$/ ? $sign.oct : $sign.$_*1;
}
Greetings
-- Andreas
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Andreas Kamentz
Electrical Engineer / SW
Antenna Engineering
[EMAIL PROTECTED]
Tel: (+49) 5063.990.541
Fax: (+49) 5063.990.99541
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TecCenter
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-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Siebe Tolsma
Sent: Thursday, June 30, 2005 5:31 PM
To: Joe Discenza; perl-win32-users@listserv.ActiveState.com
Subject: Re: Test if string is a number?
How about regexp?
/^\-?(\d+\.?\d*|\.\d+)$/
- Original Message -
From: Joe Discenza
To: Chris Wagner ; perl-win32-users
Sent: Thursday, June 30, 2005 4:48 PM
Subject: RE: Test if string is a number?
Chris Wagner wrote, on Thu 6/30/2005 08:48
: Wow there's been a lot of heavy duty code proposed to do something so
: simple. The answer is in how Perl converts between the two.
:
: print is a number if $var eq $var + 0;
: print not a number if $var ne $var + 0;
Except if $var is, say, '0.00'. Then $var + 0 is '0', and won't eq $var.
Joe
==
Joseph P. Discenza, Sr. Programmer/Analyst
mailto:[EMAIL PROTECTED]
Carleton Inc. http://www.carletoninc.com
574.243.6040 ext. 300fax: 574.243.6060
Providing Financial Solutions and Compliance for over 30 Years
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RE: Test if string is a number?
At 09:48 AM 6/30/05 -0500, Joe Discenza wrote: Except if $var is, say, '0.00'. Then $var + 0 is '0', and won't eq $var. 0.00 is not a valid internal representation of a number. That can only exist as a string. Same goes for 1e7. That is a print formated number, not a valid internal number. $var = 1e7 and print $var - 1000. $var = 0.00 and print $var - 0. If u want to include numberish strings then u need some eval's to digest the various number formats. ... if eval $var eq $var + 0; -- REMEMBER THE WORLD TRADE CENTER ---= WTC 911 =-- ...ne cede males 0100 ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
RE: Test if string is a number?
[EMAIL PROTECTED] wrote: 0.00 is not a valid internal representation of a number. That can only exist as a string. I think u need to re-read the subject of this thread. - Mark. ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
RE: Test if string is a number?
Title: RE: Test if string is a number? Chris Wagner wrote, on Thu 6/30/2005 12:41 : At 09:48 AM 6/30/05 -0500, Joe Discenza wrote:: Except if $var is, say, '0.00'. Then $var + 0 is '0', and won't eq $var.:: 0.00 is not a valid internal representation of a number. That can only: exist as a string. Same goes for "1e7". That is a print formated number,: not a valid internal number. $var = 1e7 and print $var - 1000. $var =: 0.00 and print $var - 0. If u want to include "numberish" strings then u: need some eval's to digest the various number formats. ... if eval $var eq: $var + 0; IIRC (no longer have the message), the OP had *string* data to check for numerics. Your method would miss, say, a CSV full of prices if they ended ".00" or ".50". I bet you're right that "eval($var) eq $var + 0" works; have you benchmarked it against all the other (regex, e.g.) methods presented? Joe == Joseph P. Discenza, Sr. Programmer/Analyst mailto:[EMAIL PROTECTED] Carleton Inc. http://www.carletoninc.com 574.243.6040 ext. 300 fax: 574.243.6060Providing Financial Solutions and Compliance for over 30 Years ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
RE: Test if string is a number?
At 12:16 PM 6/30/05 -0500, Joe Discenza wrote:
I bet you're right that eval($var) eq $var + 0 works; have you
benchmarked it against all the other (regex, e.g.) methods presented?
I haven't benchmarked it but I can garuntee that it's faster than a regex.
Anything's faster than that. ;) This should cover everything:
foreach $var (1e7, 0, 5, 6, 0.00, -4, abc, f4fc) {
if ($var eq $var + 0) {
print $var is a pure number\n;
}
elsif (eval $var eq $var + 0) {
print $var is a number\n
}
else {
print $var is not a number\n;
}
}
1e7 is a number
0 is a pure number
5 is a pure number
6 is a pure number
0.00 is a number
-4 is a pure number
abc is not a number
f4fc is not a number
--
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RE: Test if string is a number?
Title: RE: Test if string is a number? Chris Wagner wrote, on Thu 6/30/2005 14:41 : At 12:16 PM 6/30/05 -0500, Joe Discenza wrote:: I bet you're right that "eval($var) eq $var + 0" works; have you: benchmarked it against all the other (regex, e.g.) methods presented?:: I haven't benchmarked it but I can garuntee that it's faster than a regex.: Anything's faster than that. ;) This should cover everything: Thanks for playing. I compared your function with a regex I whipped up (/^[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?$/,which gave the same results, except for distinguishing "pure" numbers, on your dataset): Benchmark: timing 10 iterations of chris, regex... chris: 12 wallclock secs (11.86 usr + 0.00 sys = 11.86 CPU) @ 8432.41/s (n=10) regex: 2 wallclock secs ( 1.56 usr + 0.00 sys = 1.56 CPU) @ 63979.53/s (n=10) Regex is pretty fast. Eval is usually pretty slow. Joe == Joseph P. Discenza, Sr. Programmer/Analyst mailto:[EMAIL PROTECTED] Carleton Inc. http://www.carletoninc.com 574.243.6040 ext. 300 fax: 574.243.6060Providing Financial Solutions and Compliance for over 30 Years ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
Re: Test if string is a number?
Joe Discenza wrote:
Chris Wagner wrote, on Thu 6/30/2005 14:41
: At 12:16 PM 6/30/05 -0500, Joe Discenza wrote:
: I bet you're right that eval($var) eq $var + 0 works; have you
: benchmarked it against all the other (regex, e.g.) methods presented?
:
: I haven't benchmarked it but I can garuntee that it's faster than a regex.
: Anything's faster than that. ;) This should cover everything:
Thanks for playing. I compared your function with a regex I whipped up
(/^[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?$/, which gave the same
results, except for distinguishing pure numbers, on your dataset):
Benchmark: timing 10 iterations of chris, regex...
chris: 12 wallclock secs (11.86 usr + 0.00 sys = 11.86 CPU) @
8432.41/s (n=10)
regex: 2 wallclock secs ( 1.56 usr + 0.00 sys = 1.56 CPU) @
63979.53/s (n=10)
Regex is pretty fast. Eval is usually pretty slow.
1) I don't consider Chris's solution to be a legit solution until it
doesn't issue any warnings or error messages.
2) I got these numbers from my test (strict/warnings turned off) :
Rate RE STRTOD IFLLN
RE 7530/s -- -72% -75% -75%
STRTOD 26948/s 258% -- -10% -11%
IF 29782/s 295%11% ---2%
LLN30274/s 302%12% 2% --
looks_like_number seems to be the winner.
I used the same two lines of code in each sub to clean up
the input:
$var =~ s/^\s+//; $var =~ s/\s+$//;
return 0 if not defined $var or $var eq '';
use strict;
use warnings;
use Scalar::Util qw(looks_like_number);
use POSIX qw(strtod);
use Benchmark qw(timethese cmpthese);
# test output of subs before benchmarking
foreach my $sub (\sub1, \sub2, \sub3, \sub4) {
foreach (1e7, 0, 5, 6, 0.00, -4, abc, f4fc, '+.1', undef) {
my $val = defined $_ ? $_ : 'undef';
my $ret = $sub ($_);
print $ret ? sub1 ($ret): '$val' is a number\n :
sub1 ($ret): '$val' is not a number\n;
$ret = $sub ($_);
print $ret ? sub2 ($ret): '$val' is a number\n :
sub2 ($ret): '$val' is not a number\n;
$ret = $sub ($_);
print $ret ? sub3 ($ret): '$val' is a number\n :
sub3 ($ret): '$val' is not a number\n;
$ret = $sub ($_);
print $ret ? sub4 ($ret): '$val' is a number\n :
sub4 ($ret): '$val' is not a number\n;
}
}
no warnings;# needed for Chris solution
no strict; # needed for Chris solution
my $count = 100;
cmpthese ($count, {
RE = 'main (\sub1)',
IF = 'main (\sub2)',
STRTOD = 'main (\sub3)',
LLN = 'main (\sub4)',
});
sub main {
my $cref = shift;
foreach (1e7, 0, 5, 6, 0.00, -4, abc, f4fc, '+.1', undef) {
$cref ($_);
}
}
sub sub1 {
my $var = shift;
$var =~ s/^\s+//; $var =~ s/\s+$//;
return 0 if not defined $var or $var eq '';
if ($var eq $var + 0) {
return 1;
} elsif (eval $var eq $var + 0) {
return 2;
}
return 0;
}
sub sub2 {
my $var = shift;
$var =~ s/^\s+//; $var =~ s/\s+$//;
return 0 if not defined $var or $var eq '';
return 1 if $var =~ /^[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?$/;
return 0;
}
sub sub3 {
my $var = shift;
$var =~ s/^\s+//; $var =~ s/\s+$//;
return 0 if not defined $var or $var eq '';
$! = 0;
my ($num, $unparsed) = strtod ($var);
return 0 if $unparsed or $!;
return 1;
}
sub sub4 {
my $var = shift;
$var =~ s/^\s+//; $var =~ s/\s+$//;
return 0 if not defined $var or $var eq '';
# return looks_like_number ($var);
# code stripped from LLN:
return 1 if (/^[+-]?\d+$/); # is a +/- integer
return 1 if (/^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/); # a C float
return 1 if ($] = 5.008 and /^(Inf(inity)?|NaN)$/i) or
($] = 5.006001 and /^Inf$/i);
}
__END__
--
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(_/ / )// // DBE CollectiblesMailto:[EMAIL PROTECTED]
/ ) /-- o // // Castle of Medieval Myth Magic http://www.todbe.com/
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RE: Test if string is a number?
At 02:28 PM 6/30/05 -0500, Joe Discenza wrote: Regex is pretty fast. Eval is usually pretty slow. Yeah ur right about the eval. I did a triple head to head with ur regex and eval/no eval. The eq without the eval demolishes all. Rate evalRE noeval eval3397/s -- -87% -96% eval $var eq $var + 0; RE 25253/s 643%-- -72% /^[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?$/ noeval 90909/s 2576% 260% -- $var eq $var + 0; -- REMEMBER THE WORLD TRADE CENTER ---= WTC 911 =-- ...ne cede males 0100 ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
Re: Test if string is a number?
Thanks folks. I think I'll go with looks_like_number from Scalar::Util. I like to use library routines where possible. I don't know how I overlooked that, since I poked through Scalar::Util earlier. It just seems bizarre to me that something like that isn't a builtin. I mean, you can't even tell strings from numbers? I'm used to working in strongly typed languages. -- Lyle Kopnicky Software Project Engineer Veicon Technology, Inc. ___ Perl-Win32-Users mailing list Perl-Win32-Users@listserv.ActiveState.com To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
