June 22, 2012
Is this expected and good?


void main() {
    int[] array = [1, 2];
    foreach (ref const(int) x; array) {} // OK
    foreach (ref immutable(int) x; array) {} // error
}


DMD 2.060alpha:
temp.d(4): Error: argument type mismatch, int to ref immutable(int)

Thank you,
bye,
bearophile
June 22, 2012
On Friday, 22 June 2012 at 11:07:14 UTC, bearophile wrote:
> Is this expected and good?
>
>
> void main() {
>     int[] array = [1, 2];
>     foreach (ref const(int) x; array) {} // OK
>     foreach (ref immutable(int) x; array) {} // error
> }
>
>
> DMD 2.060alpha:
> temp.d(4): Error: argument type mismatch, int to ref immutable(int)
>
> Thank you,
> bye,
> bearophile

I think it's good. In this special case, the compiler can see that you can't change array behind his back. That seems not to be true in general.

June 22, 2012
Tobias Pankrath:

> I think it's good. In this special case, the compiler can see that you can't change array behind his back. That seems not to be true in general.

But aren't int implicitly castable to immutable?

Bye,
bearophile
June 22, 2012
On 22-Jun-12 16:16, bearophile wrote:
> Tobias Pankrath:
>
>> I think it's good. In this special case, the compiler can see that you
>> can't change array behind his back. That seems not to be true in general.
>
> But aren't int implicitly castable to immutable?
>

then every array is implicitly castable to tail immutable.
int[] array = [1, 2];

    foreach (ref immutable(int) x; array) {
	...
	func(arr); // arr is mutable, thus func can change x
	// so x can be at most  const
    }

-- 
Dmitry Olshansky


June 22, 2012
Dmitry Olshansky:

> then every array is implicitly castable to tail immutable.
> int[] array = [1, 2];
>
>     foreach (ref immutable(int) x; array) {
> 	...
> 	func(arr); // arr is mutable, thus func can change x
> 	// so x can be at most  const
>     }

I understand, thank you :-)

Bye,
bearophile
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