Comparing multiple conditions

[chrismassey]

Hi,

I have 3 Perl conditions:
if (($n_carry_pu eq "") || ($n_carry_pu eq $fslash)) { $top_level = "x"; }
if (substr($new_path_we, -1) eq ".") { $top_level = "x"; }

I want to make the above code simpler by combining all 3 conditions. I tried:
if (($n_carry_pu eq (("") || ($fslash))) || (substr($new_path_we, -1) eq ".") { $top_level = "x"; }

But I have had no luck.

Any help will be greatly appreciated.

Chris

 

[ishnid]

You can't do this:

$n_carry_pu eq (("") || ($fslash))

Since the empty string is considered to be a 'false' value for boolean purposes, (("")||($fslash)) always returns $fslash. To compare $n_carry_pu to both, you'll have to make both comparisons separately:

if (( $n_carry_pu eq '' ) || ( $n_carry_pu eq $fslash ) || (substr($new_path_we, -1) eq '.') ) {
   $top_level = 'x';
}

Also, the parentheses in your original code don't match up. You've one more opening parenthesis than closing ones.

 

[chrismassey]

Nice one, thanks for that ishnid,

I have made the comparisons separately after all.

Thanks

 

[MillerH]

This is how the default settings of Perl::Tidy would suggest that you format that if statement:

[olive][b]if[/b][/olive] [red]([/red]   [blue]$n_carry_pu[/blue] eq [red]"[/red][purple][/purple][red]"[/red]
    || [blue]$n_carry_pu[/blue] eq [blue]$fslash[/blue]
    || [url=http://perldoc.perl.org/functions/substr.html][black][b]substr[/b][/black][/url][red]([/red] [blue]$new_path_we[/blue], -[fuchsia]1[/fuchsia] [red])[/red] eq [red]"[/red][purple].[/purple][red]"[/red] [red])[/red]
[red]{[/red]
    [blue]$top_level[/blue] = [red]"[/red][purple]x[/purple][red]"[/red][red];[/red]
[red]}[/red]

- Miller

 

[ishnid]

Thanks Miller. I couldn't remember if 'eq' and 'ne' bound higher than '||' or not, so I went for the safe option.

 

[MillerH]

Understood. If all else fails, check out perlop - Operator Precedence and Associativity. Pretty much the only times I need parenthesis are for lists, subroutine parameters and mathematical operator precedence. The order of operations generally follows what you'd want.

- Miller

 

[KevinADC]

another way to code those multiple choice conditions using the ternary operator:

$top_level = $n_carry_pu eq "a" ? 'x' :
             $n_carry_pu eq $fslash ? 'x' :
             substr( $new_path_we, -1 ) eq "." ? 'x' : 'y';

where 'y' equals the default value. If $top_level already has a default value substitute $top_levy for 'y' at the end.

------------------------------------------
- Kevin, perl coder unexceptional!

 

[chrismassey]

Hey cheers Miller & Kevin,

I am trying to shorten a perl script because its unneccessarily long at the moment :s.

I appreciate the help, i've managed to clean alot of my conditions up now.

Chris