unless statements

Unless statements allow you to say unless something is true do this. For example:

$value=20;
unless($divisor==0){      #so long as the $divisor isn't equal to 0
  $value=$value/$divisor; #go ahead and divide $value by $divisor
} else {
  $divisor=1;             #otherwise set $divisor to 1
}

If you've got that I suggest you take a look at while loops

Comment on unless statements

Replies are listed 'Best First'.
Re: unless statements by htoug (Deacon) on Feb 08, 2005 at 11:09 UTC
It is a matter of taste (and style), but I only use `unless` without the `else`-clause. If you have the `else`, then you could just as well use a normal `if` and get better readability - it's more like waht everyone is used to. But in a standalone `if (!(some_complicated_expression))` the use of `unless` lets you remove one pair of parenthesis and lets the poor smuck reading the code have one less thing to worry about. I would rewrite your example as `$value=20; if ($divisor!=0){ #so long as the $divisor isn't equal to 0 $value=$value/$divisor; #go ahead and divide $value by $divisor } else { $divisor=1; #otherwise set $divisor to 1 }` [download] Now the statement says the same as the comment (in your code it should have been `#unless the $divisor isn't equal to 0` - 'so long' indicates a repetition IMHO).	[reply] [d/l] [select]
Re^2: unless statements by Anonymous Monk on Jul 01, 2005 at 16:15 UTC
Hello , well i think unless is a loop and things like : if ($divisor!=0){ doesn't work rather than using unless if will procedes the action for one time but unless will keep procedes the same things unless the statment goes wrong that's what i think	[reply]
what is benefit of unless ? by Anonymous Monk on Feb 05, 2005 at 11:34 UTC
I think unless statements are similar to if statements.But if-else stmt gives us more flexibility then unless.So is there any specific use of this . please reply soon. regards, barun parichha	[reply]
Re: what is benefit of unless ? by holli (Abbot) on Feb 05, 2005 at 17:43 UTC
`$ cat input foo bar $ perl -ne 'print unless /^$/../^$/' input foo bar $ perl -ne 'print if not /^$/../^$/' input foo bar $ perl -ne 'print if ! /^$/../^$/' input foo bar` [download] The unless statement is equivalent to if not, but is different from if ! due to the associativity and precedence rules covered in perlop. A benefit of this behavior allows the reduction of runs of blank lines to a single blank line. taken from here	[reply] [d/l]
Re: what is benefit of unless ? by Anonymous Monk on Feb 05, 2005 at 12:04 UTC
You can use "else" with "unless". "unless" means "if not", so it reverses the meaning of an "if" comparison. See perlsyn for details. Please read Where should I post X? and How (Not) To Ask A Question.	[reply]
equivalent code for unless by Anonymous Monk on Feb 05, 2005 at 12:15 UTC
is this the equivalent code for " unless(condition)" ? if !(condition) { ... ... } else { ... ... } reply soon, barun parichha	[reply]
Re: equivalent code for unless by merlyn (Sage) on Feb 05, 2005 at 13:04 UTC
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Re: what is benefit of unless ? by prasadbabu (Prior) on Feb 05, 2005 at 12:12 UTC
It is not similar statement. `$a = 10; print "if stmt true" if ($a == 10); print "unless" unless ($a == 10);` [download] Prasad	[reply] [d/l]

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