if/else syntax

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

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Re: if/else syntax by ikegami (Patriarch) on Jun 26, 2009 at 15:08 UTC
Brackets are mandatory on `if` statements in Perl. Note that, unlike C and Pascal, these are defined in terms of BLOCKs, not statements. This means that the curly brackets are required--no dangling statements allowed. The optionality of the brackets is a source of problems for C. In Perl 6, it's the parens around the condition that are optional. They're already optional around the condition of statement modifiers in Perl 5. `someFunc() if ($someVar == $anotherVar); someFunc() if $someVar == $anotherVar; # Same thing` [download]	[reply] [d/l] [select]
Re^2: if/else syntax by Anonymous Monk on Jun 26, 2009 at 15:48 UTC
so if the brackets are there to avoid problems, the C/perl syntax `(a?b:c)` also has those problems right ?	[reply] [d/l]
Re^3: if/else syntax by ikegami (Patriarch) on Jun 26, 2009 at 16:49 UTC
(a?b:c) also has those problems right ? No, because the "`:`" isn't optional like `else` is, and because people don't indent the conditional operator like they would an if/else. It has a different problem, though. A frequent mistake with the conditional operator is to use it as follows: `$c ? $x = $i : $y = $j;` [download] The above means `( $c ? $x = $i : $y ) = $j;` [download] but people expect it to mean `$c ? ($x = $i) : ($y = $j);` [download]	[reply] [d/l] [select]
Re^4: if/else syntax by Anonymous Monk on Jun 26, 2009 at 17:05 UTC
Re^3: if/else syntax by Crackers2 (Parson) on Jun 26, 2009 at 16:10 UTC
I don't think so. With if/else: `if a if b c else d` [download] could mean `if a { if b { c } else { d } } or if a { if b { c } } else { d }` [download] With the ternary operator that would be `a ? b ? c : d : () and a ? b ? c : () : d` [download] so there's no abmbiguity.	[reply] [d/l] [select]
Re^4: if/else syntax by gwadej (Chaplain) on Jun 26, 2009 at 16:44 UTC
Re^5: if/else syntax by Anonymous Monk on Jun 26, 2009 at 17:01 UTC
Re^5: if/else syntax by ikegami (Patriarch) on Jun 26, 2009 at 17:20 UTC
Some notes below your chosen depth have not been shown here
Re^4: if/else syntax by Anonymous Monk on Jun 26, 2009 at 16:27 UTC
Re^5: if/else syntax by Transient (Hermit) on Jun 26, 2009 at 17:21 UTC
Re^3: if/else syntax by dreadpiratepeter (Priest) on Jun 26, 2009 at 15:51 UTC
what you are looking for is: `if ($cond==1) { do_good(); } else { do_bad(); }` [download] -pete "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."	[reply] [d/l]
Re: if/else syntax by suaveant (Parson) on Jun 26, 2009 at 15:07 UTC
If you want an "else" with an if, you need the brackets, "if" after the statement is a modifier, not a control block... if you just need the else, use unless `print "OK\n" unless $a == 1;` [download] Update: I suppose you could do `print "OK\n" if $a == 1; print "Not OK\n" unless $a == 1;` [download] But don't. ;) - Ant - Some of my best work - (1 2 3)	[reply] [d/l] [select]
Re: if/else syntax by Herkum (Parson) on Jun 26, 2009 at 16:03 UTC
The closest thing I can think of, is using a return statement in your call. So you have to be specific in your usage. FYI, I use this syntax all the time because it is very easy to read. `sub checkConditions { my $value = shift; return someFunc() if $value == 0; return otherFunc(); }` [download]	[reply] [d/l]
Re: if/else syntax by massa (Hermit) on Jun 26, 2009 at 17:46 UTC
you could do `$somevar == $anothervar and (someFunc(), 1) or anotherFunc();` [download] but please don't. it's awful. []s, HTH, Massa (κς,πμ,πλ)	[reply] [d/l]
Re: if/else syntax by Marshall (Canon) on Jun 27, 2009 at 04:56 UTC
Perl has a nice thing that allows "reversing" the if and a SINGLE action statement. single_action_statement...if(blah)... This is not what you have here! And I would argue that your code C code is bad because it is not clear. better: `if ( $someVar == $anotherVar ) { someFunc(); } else { anotherFunc(); }` [download] You are making a HUGE mistake if you think that number of source code lines equals efficiency - I would recommend some advanced C classes or ASM classes. The compiler whether it be "Perl" or "C" can deal with the above construct VERY efficiently.	[reply] [d/l]
Re^2: if/else syntax by massa (Hermit) on Jun 29, 2009 at 13:53 UTC
One can start a holy war (specially in a Perl forum) about more characters/lines versus readability/maintainability. I, for instance, am of the school of thought that goes "as long it does not _obscure_ the meaning, the shorter the better". That way, I prefer `$someVar == $anotherVar ? someFunc() : anotherFunc()` [download] over _any_ of the alternatives because it's elegant, concise and _absolutely_ clear. ikegami pointed out to me that `?:` can get really messy really fast. I agree. But in the case at hand, it's unbeatable IMHO. []s, HTH, Massa (κς,πμ,πλ)	[reply] [d/l] [select]
Re^3: if/else syntax by Marshall (Canon) on Jun 29, 2009 at 14:26 UTC
I don't want to start a holy war either! Your formulation is completely acceptable to me. For a short thing like this, I use it all the time. The OP said that he/she didn't like this syntax. If so, then use if{}else{} (my opinion). I don't see a problem here. As a matter of style, I would put parens around the conditional, but that is a very minor point.	[reply]