Const ref and rvalues again...

[martin]

On Monday, 12 November 2012 at 23:38:43 UTC, luka8088 wrote:
> What about making this a default behavior and introducing a new 
> keyword if the function wants to modify the argument but it is 
> not ref (pass by value) ? The reason I think that this should 
> be a default behavior because not many functions actually 
> modify their arguments and so it leaves a lot of space for 
> optimization.
>
> For example:
>
> void f (int x, val int y, ref int z) {
>   x = 1; // x is not copied
>          // compiler throws an error, x is not passed by value
>          // and therefor could not / should not be changed
>   y = 2; // ok, y is copied
>   z = 3; // ok, z is a reference
> }

Your proposal isn't really related to this thread's topic, but I 
understand what you mean (although your code comments distract me 
a bit):

void f(const int x, int y, ref int z); =>
void f(int x, val/mutable int y, ref int z);

I use const/in ;) parameters a lot in my code too to prevent 
accidental modifications, so my function signatures may be more 
compact by treating normal pass-by-value parameters as const if 
not denoted with a special keyword. I guess it wouldn't be very 
important for optimization though because I'd expect the 
optimizer to detect unchanged parameters. Anyway, your proposal 
would completely break existing code.