Re: Using ternary operator as lvalue in push

Did you happen to see what your friend was testing? Or what version he was using? There's been a bug for a long time that something like push CONSTANT-EXPRESSION ? @a : @b, LIST; works when it shouldn't, where CONSTANT-EXPRESSION is a constant or operations that result in a constant, like:

use constant OS => $^O;
push OS eq "linux" ? @a : @b, "tux";
[download]

Don't rely on this to continue working: it's clearly a bug. Always use the @{ expression resulting in an arrayref } instead.

Using non-constant expressions before the ?, it fails for me on 5.6.2, 5.8.0, 5.8.8, and 5.9.5.

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Re^2: Using ternary operator as lvalue in push by dada (Chaplain) on Aug 01, 2007 at 09:54 UTC
ouch... I'm oha's friend :-) of course, I tested it with: `# This is perl, v5.8.7 my @a = (1,2,3); my @b = (4,5,6); push 1==1 ? @a : @b, "foo"; print "a=@a b=@b\n";` [download] I even counter-checked (!) it with: `push 1==0 ? @a : @b, "foo";` [download] to verify that the "foo" was pushed into @b. of course, such stupid conditionals are optimized away. sorry for fooling myself, oha, and probably others. shame on me :-) cheers, Aldo King of Laziness, Wizard of Impatience, Lord of Hubris	[reply] [d/l] [select]
Re^3: Using ternary operator as lvalue in push by FunkyMonk (Bishop) on Aug 01, 2007 at 10:38 UTC
Compile time constant removal magic. `perl -MO=Deparse play` produces: `my(@a) = (1, 2, 3); my(@b) = (4, 5, 6); push @a, 'foo'; print "a=@a b=@b\n";` [download] /msg self Read ALL the post before replying	[reply] [d/l] [select]
Re^2: Using ternary operator as lvalue in push by oha (Friar) on Aug 01, 2007 at 09:17 UTC
could be, i will ask him. i used a code that could be optimized by compiler: `my $c = 1; push $c>0 ? @a : @b, "foo";` [download] maybe different settings would allow the compiler to reduce the condition at compile-time (my friend case) resulting in `push @a, "foo";` [download] that will explain those behaviour Oha	[reply] [d/l] [select]
Re^3: Using ternary operator as lvalue in push by ikegami (Patriarch) on Aug 01, 2007 at 14:19 UTC
`my $c = 1; push $c>0 ? @a : @b, "foo";` [download] is not optimized by the compiler. It only folds constants. `$c` is not a constant. On the other hand, the following would be optimized: `use constant c => 1; push c>0 ? @a : @b, "foo";` [download]	[reply] [d/l] [select]