Nested Ternary Operators

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

Alright, here's what I have:

$ref_to_all_lines_in_file   # contains all lines in file minus those i
+n %hash or @array
@array;                     # contains some lines from the file
%hash;                      # contains array refs
$hash_count;                # totals all arrays referenced in %hash
$array_count;               # scalar(@array);
$ref                

if($hash_count) { $ref = \%hash; }
elsif($array_count) { $ref = \@array; }
else { $ref =  $ref_to_all_lines_in_file; }
[download]

so that works and all.. just thought it'd be neater to do a nested ternary operator like:

$ref = $hash_count ? \%hash : { $array_count ? \@array : $ref_to_all_l
+ines_in_file };
[download]

however, this doesn't seem to be working.. should it be possible to do this? or I am just high off the paint fumes meandering in from the construction on the other side of the wall? :)

-brad..

Comment on Nested Ternary Operators Select or Download Code

Replies are listed 'Best First'.
(jcwren) Re: Nested Ternary Operators by jcwren (Prior) on Nov 20, 2000 at 23:28 UTC
It probably doesn't work because you're using braces, instead of parenthesis. Which means that you're setting $ref to an anonymous hash, if $hash_count is zero. Consider this code, and it's output: `#!/usr/local/bin/perl -w use strict; use Data::Dumper; { my $a = 0; my $b = 1; my $c = 2; # # $a is 0, so the second term will be evaluated # $b is meaningless, and just used as a place holder # $c is 2, so 3 should be the answer. # my $right = $a ? $b : ($c ? 3 : 4); my $wrong = $a ? $b : {$c ? 3 : 4}; print "Right=", $right, "\n"; print "Wrong=", $wrong, "\n"; print Dumper ([\$right]); print Dumper ([\$wrong]); }` [download] `Odd number of elements in hash assignment at t line 17. Right=3 Wrong=HASH(0x80e6154) $VAR1 = [ \3 ]; $VAR1 = [ \{ 3 => undef } ];` [download] --Chris e-mail jcwren	[reply] [d/l] [select]
Re: Nested Ternary Operators by Dominus (Parson) on Nov 21, 2000 at 00:26 UTC
The ternary operator was designed (by Thompson and Ritchie, the inventors of C) to make this sort of thing simple. Just use: `$ref = $hash_count ? \%hash : $array_count ? \@array : $ref_to_all_lines_in_file;` [download] Note that no parentheses of any sort are necessary.	[reply] [d/l]
Re: Nested Ternary Operators by KM (Priest) on Nov 20, 2000 at 23:22 UTC
What do you mean "isn't working"? Do you get an error? The following works fine for me (5.6): `my $foo = 0; my $baz = 0; my $bar = $foo ? 1 : ($baz ? 4 : 2); print $bar;` [download] Cheers, KM	[reply] [d/l]