Re^5: Pre vs Post Incrementing variables

[BrowserUk]

Mind you, it might make explaining this one a tad awkward :)

$i = 0; print ++${\++$i}, 0+ ++$i, 0+ ++$i, ++${\++$i};;
6 3 4 6

[repellent]

The argument list to print is evaluated from left-to-right. ++${\++$i} is merely incrementing $i twice and returning an alias to $i.


$i = 0; print ++${\++$i}, 0+ ++$i, 0+ ++$i, ++${\++$i};;
              ^              ^        ^     ^
             (1)            (2)      (3)   (4)


(1) & (4) return aliases to $i. Since $i has been incremented six times, we get 6 for both of them.

(2) & (3) return copies to $i because of the zero additions 0+. We get 3 for (2) after three increments, and 4 for (3) with one more increment.

[BrowserUk]

You appear to be saying that the ability to describe what the implementation does, justifies why it does it that way.

The fact that this:

$i=0; print $n = ++$i, $m = ++$i;;
1 2

produces a different result to this:

$i=0; print ++$i, ++$i;;
2 2

Is just plain weird. Some, including me, would say 'broken'.

Justifying the weirdness by saying "that's what it does", kinda reminds of Apple's "You're holding it wrong." explanation of Antennagate.

[repellent]

No, I made no implied justification thus far.

The root of my reply was merely to reveal my experimentation with assigning the return of (++$i) to some value (since I also ran into the same error message you got).

Then, I attempted to explain the snippet you posted so that others may find it helpful to see what's going on.

My opinion? Yeah, the lvalue stuff is confusing and I don't quite see its usefulness. I would expect the behavior the OP expected.