deep usage of if-else!!

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

hi,
I have one app in wich to do my job i have to make alot of if/unless-else chained checks and in most of the cases the actions after that are no more than 3, not everytime but ..!!
Because after a while they become very ugly I want to find a way to simplify the things and make the code more strightforward/non-hairy ;).
But let me show u simple example

$o->check(...);
unless ($o->state) {
   action..
} else {
   $o->check(...);
   unless ($o->state) {
     action....
     $o->blah()
     if ($o->state) {
        actions..check..
          unless($r->state) {
             and so on...deeper and deeper...
          }
     }
   }
}
[download]

Most of the checks are on $object->state(), but not nececerily.
For the sake of it things become more underadable when I add alot of comments to clarify the things ;))
I'm looking for an idea how to make this easier for the users of my module. So if the idea adds more complex code/behavior on the Class i'm building it is doable. My main goal is to simplify the task of the other programmers.
I was thinking something on the line of prolog like syntax or I see some lang have 'assert', (cant figure out the idea exactly) !!. But it has to stay perl, not something parsable, 'cause sometimes there is very convulved logic to be added.

10x alot in advance

Comment on deep usage of if-else!! Download Code

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Re: deep usage of if-else!! by GrandFather (Saint) on May 01, 2006 at 19:42 UTC
In this situation I try if possible to take advantage of early exits: If this is inside a `while` or `for` loop use `last` as the final statement in any block preceeding an else and omit the else. If it is inside a `sub` and there are no statements following the topmost if, use `return` in place of `last` in a similar fashion. If need be change the sense of the test to take advantage of this technique. For example, assuming a `sub`: `$o->check(...); unless ($o->state) { action.. return; } $o->check(...); return if $o->state; action.... $o->blah() return unless $o->state; actions..check.. return if $r->state; and so on... at the same level` [download] DWIM is Perl's answer to Gödel	[reply] [d/l] [select]
Re: deep usage of if-else!! by davidrw (Prior) on May 01, 2006 at 18:06 UTC
Not sure i really like this, but it's logicaly equivalent and cleans it up a little .. `if( do{$o->check(...); ! $o->state} ){ action.. }elsif( do{$o->check(...); ! $o->state} ){ action.... $o->blah() if ($o->state) { actions..check.. unless($r->state) { and so on...deeper and deeper... } } }` [download] It's hard to say w/o knowing what the check() and state() methods do and their return values.. In general, I would say to push things off into methods .. `$o->check(...); unless ($o->state) { $o->actionSet1; } else { $o->check(...); unless ($o->state) { $o->actionSet1; } }` [download] So what does the check() method return? if it did `return $this->state` then things simplify alot: `unless ( $o->check(...) ) { action.. } else { unless ( $o->check(...) ) { action.... $o->blah() if ($o->state) { actions.. unless( $o->check(...) ) { and so on...deeper and deeper... } } } }` [download]	[reply] [d/l] [select]
Re^2: deep usage of if-else!! by rootcho (Pilgrim) on May 01, 2006 at 18:27 UTC
yes $o->check() returns 0 or 1, but in most of the cases it is too long i.e. parameter passed to it, that is why i'm using $o->state. But yes as u and Hue-Bond said I can see which are the most frequently combination of checks and actions and separate them into methods, this way I will shorten things abit.(before i read your replies i figured out to shorten one of them). But then, i can do this for just several of them, otherwise i will go into the trap of too-many-methods ;) That is why i was wondering that probably someone already invented something along these lines ;)) thanx for your replies	[reply]
Re^3: deep usage of if-else!! by davidrw (Prior) on May 01, 2006 at 18:54 UTC
yes $o->check() returns 0 or 1, but in most of the cases it is too long i.e. parameter passed to it too long? so? that's fine, or bundle the params into a hash, or store in the object: `if( ! $obj->check( blah => 1, stuff => 2, foo => 'bar', ... )){ ... } my %params = ( blah => 1, stuff => 2, foo => 'bar', ... ) if( ! $obj->check(%params) ){ ... } $obj->blah(1); $obj->stuff(2); $obj->foo('bar'); ... if( ! $obj->check() ){ ... }` [download]	[reply] [d/l]
Re^2: deep usage of if-else!! by Anonymous Monk on May 01, 2006 at 19:24 UTC
`if( do{$o->check(...); ! $o->state} ){ action.. }` [download] Why the `do` block instead of a comma? `if($o->check(...), ! $o->state} ){ action.. }` [download] ...not that I think that putting multiple things inside the conditional of an `if` is a good idea.	[reply] [d/l] [select]
Re: deep usage of if-else!! by Hue-Bond (Priest) on May 01, 2006 at 17:51 UTC
You should try to divide that piece of code in logical, reusable parts that can be abstracted into functions. That way, the nesting won't go very deep and your program will gain in readability and maintainability. -- David Serrano	[reply]