Array as an argument, ambiguous behaviour.

[Sergei Nosov]

On Wednesday, 29 January 2014 at 14:48:12 UTC, Cooler wrote:
>> If, however, in fun3 you change the size of the array - it may 
>> reallocate. Like, if you're appending to `x` - it will 
>> allocate a new array and make x point to it. Now `a` and `x` 
>> point to distinct arrays. And any change you do using `x` 
>> won't be seen by `a`. And, yes, this is the intended behavior.
>
> That exactly what am i asking for!
> You have to know the body of fun3() to predict what happened 
> with 'a'.
> When I call fun() there are 3 intentions:
> 1. I want just send the contents of 'a' to fun(). It can be 
> done by a.dup, or you must sure that fun() has 'in' qualifier 
> for it's argument.
> 2. I want fun() change content of 'a' array. This can be done 
> by ensuring fun() has 'ref' qualifier for it's argument.
> What intention should I have to call fun3()?

E.g. you want fun3 to change the content of the array, but you 
don't want it to change the pointer.

Consider,

void fun2(ref int[] x)
{
    x = null;
}

void fun3(int[] x)
{
    x = null;
}

void main()
{
    int[] a = [1, 2, 3];
    fun3(a);
    assert(a);
    fun2(a);
    assert(!a);
}