Perl compare

waytoperl has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Perl compare by davido (Cardinal) on Sep 26, 2014 at 02:30 UTC
This line is wrong: `if ($number4 == 1,2) {` [download] I think you probably expected that `$number4` will compare to 1 or to 2, and that if it is equal to either 1 or 2 you will have a Boolean "true" condition. But what really happens is that `$number == 1` is evaluated, and then the result is thrown away. Then 2 is evaluated, and its value in a Boolean context turns out to be "true". So your conditional will always be true. Consider this example: `print "Yes!\n" if ( 1 == 2, 3 );` [download] The outcome will be "Yes!", because even though the conditional `1==2` is false, that evaluation is thrown away, and the "3" is evaluated numerically in Boolean context, and that will always be "true". You probably want to say something like this: `if( grep { $number4 == $_ } 1, 2 ) {...` [download] Or more simply... `if( $number4 == 1 \|\| $number4 == 2 ) { ...` [download] Or more legibly: `use List::Util 'any'; # ......... if( any { $number4 == $_ } 1, 2 ) {...` [download] Dave	[reply] [d/l] [select]
Re^2: Perl compare by waytoperl (Beadle) on Sep 26, 2014 at 04:25 UTC
`You probably want to say something like this: if( grep { $number4 == $_ } 1, 2 ) {...` [download] `use List::Util 'any'; # ......... if( any { $number4 == $_ } 1, 2 ) {...` [download] Will have Argument "1,2" isn't numeric in numeric eq <==> .... `Or more simply... if( $number4 == 1 \|\| $number4 == 2 ) { ...` [download] Worked without warning, since `$number4` is a list. Thanks	[reply] [d/l] [select]
Re: Perl compare ( numeric in void isn't numeric) by Anonymous Monk on Sep 26, 2014 at 01:05 UTC
Don't understand what's wrong. Please help! There are checklists for that , Basic debugging checklist Work through the list, turn on diagnostics, read the more verbose error message, use Deparse to see how perl parses your code "1,2" is not "a number" or "a string" , its "a list", its two numbers seperated by the comma operator	[reply]
Re^2: Perl compare ( numeric in void isn't numeric) by waytoperl (Beadle) on Sep 26, 2014 at 04:18 UTC
"1,2" is not "a number" or "a string" , its "a list", its two numbers separated by the comma operator it's a list `my ($num1,$num2) = split (',',$number4); if ($num1 == 1 && $num2 == 2) {....` [download] above code have no warning	[reply] [d/l]
Re^3: Perl compare ( numeric in void isn't numeric) by choroba (Cardinal) on Sep 26, 2014 at 13:36 UTC
It seems $number4 is not a list, it's a string. So, use string comparison `eq` and quote the string literals: `if ($number4 eq '1,2') { # ... }` [download] لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l] [select]
Re^3: Perl compare ( numeric in void isn't numeric) by GotToBTru (Prior) on Sep 26, 2014 at 14:33 UTC
No, a scalar can not be a list. It is a string containing two digits separated by a comma. 1 Peter 4:10	[reply]
Re: Perl compare by Jenda (Abbot) on Sep 26, 2014 at 10:02 UTC
Numeric literals in Perl and any other programming language I've ever heard of use decimal dots, not commas. Irrespective of locale settings. `if ($number4 == 1.2) {` [download] Jenda Enoch was right! Enjoy the last years of Rome.	[reply] [d/l]
Re: Perl compare by Random_Walk (Prior) on Sep 26, 2014 at 14:18 UTC
You already have some great advice on fixing your code. There is one thing I would like to add. When you have a construct like this: `my ($number1,$number2,$number3,$number4) = split /\t/;` it is time to learn about arrays. `use strict; use warnings; ... my @numbers = split /\t/; if ($number[3] == 42) { print "I got the answer\n"; } else { print "What was the question?\n"; } ...` [download] Note Perl arrays start with index 0 as the first element, so $numbers3 is the fourth number. You'll get used to it. Cheers, R. Pereant, qui ante nos nostra dixerunt!	[reply] [d/l] [select]
Re: Perl compare by Anonymous Monk on Sep 26, 2014 at 15:34 UTC
waytoperl, as you can tell you're getting very varied responses depending on different interpretations of what you've posted here. What is missing is the full output, specifically that of `print "$number4\n";`, as well as a sample of the input data. Please read and follow the advice in How do I post a question effectively?	[reply] [d/l]
Re^2: Perl compare by waytoperl (Beadle) on Sep 26, 2014 at 19:26 UTC
My issue got resolved. It was list and used split to resolve. Thank you all.	[reply]