scalar values assignment

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

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Re: scalar values assignment by moritz (Cardinal) on Apr 09, 2010 at 12:32 UTC
Please read perlintro. It shows you the syntax of the `if` statement. Also note that you don't have to compare boolean values to true and false - you can just use them in an `if` statement. (And you are using an assignment anyway, not a comparison. Again read perlintro) Perl 6 - links to (nearly) everything that is Perl 6.	[reply] [d/l] [select]
Re^2: scalar values assignment by sierpinski (Chaplain) on Apr 09, 2010 at 13:02 UTC
That's true in most languages, if you're comparing whether or not a value is true or false, you don't have to explicitly add ' = true'. If you're unfamiliar with this concept, and how conditionals work, I'd strong recommend looking into general programming concepts. Not necessarily Perl, although if you're programming in Perl it would be a good place to start. Learning these basic concepts will help you pick up any programming language in the future. The concepts don't change, but the syntax does, and that's just a matter of googling and forums.	[reply]
Re^2: scalar values assignment by gogoglou (Beadle) on Apr 09, 2010 at 13:00 UTC
I've read perlintro, and i've tried something like `if ($scalar1! && $scalar2!){ then.... }` [download] still this didn't work. I also don't understand what you mean that I don't have to compare booleans to true or false. I am sorry if my questions seem a bit stupid and thank you for your time to reply to me.	[reply] [d/l]
Re^3: scalar values assignment by moritz (Cardinal) on Apr 09, 2010 at 13:12 UTC
perlintro doesn't mention a `then` belonging to an `if`, because Perl is not Visual Basic. Just write `if (defined(param('foo'))) { print "yes, we have a foo\n"; } else { print "out of luck, pal\n"; }` [download] I also don't understand what you mean that I don't have to compare booleans to true or false. The question `is $thing the same as true?` is nearly the same as `is $thing true?`. When you write `if ($thing) { ... }` then perl already asks `is $thing true?` - no need to make it more complicated by explcitly comparing it to `true` (which doesn't exist in Perl 5 anyway).	[reply] [d/l] [select]
Re^3: scalar values assignment by Anonymous Monk on Apr 09, 2010 at 13:10 UTC
The actual error message should be telling you where to look. Were you trying to form a NAND operator? `!&&` isn't legit. Also, the not operator (`!`) needs something to negate at the end of your conditional.	[reply] [d/l] [select]
Re: scalar values assignment by AR (Friar) on Apr 09, 2010 at 13:55 UTC
In addition to what the other monks have said, I want to mention that you used `=` in your example. `=` is for assignment, not comparison. If you're comparing integers, you'll want to use `==`. If you're comparing stings, you'll want to use `eq`. Note: there are other problems in gogoglou's pseudo example, but I'm choosing to ignore them because they have mostly been addressed.	[reply] [d/l] [select]
Re: scalar values assignment by nvivek (Vicar) on Apr 09, 2010 at 13:05 UTC
If you want to check whether that particular scalar is defined or not.You can simply use it in the if statement as follows. `if($scalar) { statements } else { statements }` [download] If you want to check if it is undef,then you can use unless or simple else for the above if statement. For inverse of if,you can also use unless.	[reply] [d/l]
Re^2: scalar values assignment by almut (Canon) on Apr 09, 2010 at 13:19 UTC
`if($scalar) ...` [download] Strictly speaking, that would test whether `$scalar` is true, not whether it's defined. `0` or `""`, for example, evaluate to false, but are considered "defined". Test defined instead.	[reply] [d/l] [select]