On Tuesday, 23 July 2013 at 16:34:54 UTC, John Colvin wrote:
> void foo(ref int a)
> {
> 	a = 5;
> }
>
> void main()
> {
> 	int a = 0;
> 	int* aptr = &a;
> 	
> 	foo(*aptr);
> 	assert(a == 5);
> 	
> 	a = 0;
> 	
> 	int b = *aptr;
> 	foo(b);
> 	assert(b == 5);
> 	assert(a == 0);
> }
>
> The fact that adding an explicit temporary changes the semantics seems weird to me.

Thanks for the explanations people, I have now fixed a rather worrying mistake in my programming knowledge: WHAT IT ACTUALLY MEANS TO DEREFERENCE A POINTER!

Seriously, I've written programs in assembly and I still had it wrong. It's a wonder I ever wrote any correct code in my life.

On Wednesday, 24 July 2013 at 15:14:16 UTC, John Colvin wrote:
> On Tuesday, 23 July 2013 at 16:34:54 UTC, John Colvin wrote:
>> void foo(ref int a)
>> {
>> 	a = 5;
>> }
>>
>> void main()
>> {
>> 	int a = 0;
>> 	int* aptr = &a;
>> 	
>> 	foo(*aptr);
>> 	assert(a == 5);
>> 	
>> 	a = 0;
>> 	
>> 	int b = *aptr;
>> 	foo(b);
>> 	assert(b == 5);
>> 	assert(a == 0);
>> }
>>
>> The fact that adding an explicit temporary changes the semantics seems weird to me.
>
> Thanks for the explanations people, I have now fixed a rather worrying mistake in my programming knowledge: WHAT IT ACTUALLY MEANS TO DEREFERENCE A POINTER!
>
> Seriously, I've written programs in assembly and I still had it wrong. It's a wonder I ever wrote any correct code in my life.

To put the final nail in the coffin, this also works in C++:

	#include "stdio.h"

	void change(int & x) {
		x = 4;
	}

	int main(int argc, char** argv) {
		int a = 0;
		int* aptr = &a;
		change(*aptr);
		printf("%d\n", a);
	}

TBH, I was also a bit surprised because I assumed *aptr as an rvalue created a temporary, but as you mentioned, that's not how it works in assembly, so it's wrong to think it would work differently in C/C++/D.

Thanks for the post!