Increment / Decrement Operator Behavior

[Timon Gehr]

On 06/04/2012 08:36 PM, Xinok wrote:
> The increment and decrement operators are highly dependent on operator
> precedence and associativity. If the actions are performed in a
> different order than the developer presumed, it could cause unexpected
> behavior.
>
> I had a simple idea to change the behavior of this operator. It works
> for the postfix operators but not prefix. Take the following code:
>
> size_t i = 5;
> writeln(i--, i--, i--);
>
> As of now, this writes "543". With my idea, instead it would write,
> "555". Under the hood, the compiler would rewrite the code as:
>
> size_t i = 5;
> writeln(i, i, i);
> --i;
> --i;
> --i;
>
> It decrements the variable after the current statement. While not the
> norm, this behavior is at least predictable. For non-static variables,
> such as array elements, the compiler could store a temporary reference
> to the variable so it can decrement it afterwards.
>
> I'm not actually proposing we actually make this change. I simply
> thought it was a nifty idea worth sharing.

The behaviour the language requires is that the function call executes 
as if the parameters were evaluated from left to right. This is exactly 
the behaviour you observe. What is the problem you want to fix?