Re^2: Complex conditional statements

A great explanation, thanks a lot!

It raised another question, though: if one or more of those statements (A, B etc) is a print "..." statement, how can I make it print only if B is false (as in not B and A)?

UPDATE: Here's how my test code looks:

$test = $comment = 1;
($a = 3 and print "--> $a\n") if ($comment or $test) or print "no way!
+\n";
[download]

It works if ($comment or $test) gives true, but both print statements are executed if it gives false...

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Re^3: Complex conditional statements by ikegami (Patriarch) on Jun 16, 2005 at 15:12 UTC
`not B and print("...")` Unlike C, every Perl function can be used in an expression, even those that don't normally return a value. But that's moot since `print` actually does return a value: true on success, false (and sets $!) otherwise. Keep in mind that using these techniques is almost guaranteed to make your code less readable or unreadable. For expressions of that magnitude, I encourage you to treat this discussion as an academic excercise. Update: Answer to Updated question: `($a = 3 and print "--> $a\n") if ($comment or $test) or print "no way!";` is the same as `($a = 3 and print "--> $a\n") if ($comment or $test or print "no way!");` Keep in mind that `print` pretty much always returns true, so the above doesn't do what you want. You could fix it by changing the return value of `print`: `($a = 3 and print "--> $a\n") if ($comment or $test) or (print("no way!"), 0);` But that's aweful code! What's wrong with `if ($comment or $test) { $a = 3; print "--> $a\n"; } else { print "no way!\n"; }` You could shorten it a little to `$comment or $test ? ( $a = 3, print "--> $a\n" ) : print "no way!\n";` but you're starting to mess with people's ability to read your code if you do that.	[reply] [d/l] [select]

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Re^3: Complex conditional statements
by ikegami (Patriarch) on Jun 16, 2005 at 15:12 UTC

not B and print("...")

Unlike C, every Perl function can be used in an expression, even those that don't normally return a value. But that's moot since print actually does return a value: true on success, false (and sets $!) otherwise.

Keep in mind that using these techniques is almost guaranteed to make your code less readable or unreadable. For expressions of that magnitude, I encourage you to treat this discussion as an academic excercise.

Update: Answer to Updated question:

($a = 3 and print "--> $a\n") if ($comment or $test) or print "no way!";
is the same as
($a = 3 and print "--> $a\n") if ($comment or $test or print "no way!");
Keep in mind that print pretty much always returns true, so the above doesn't do what you want. You could fix it by changing the return value of print:
($a = 3 and print "--> $a\n") if ($comment or $test) or (print("no way!"), 0);
But that's aweful code! What's wrong with
if ($comment or $test) { $a = 3; print "--> $a\n"; } else { print "no way!\n"; }
You could shorten it a little to
$comment or $test ? ( $a = 3, print "--> $a\n" ) : print "no way!\n";
but you're starting to mess with people's ability to read your code if you do that.

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