Confusion over what types have value vs reference semantics

[rikki cattermole via Digitalmars-d-learn]

On 12/09/2016 3:15 AM, Neurone wrote:
> Hi,
>
> Are there universal rules that I can apply to determine what types have
> reference or value semantics? I know that for the basic primitive C
> types (int, bool, etc) has value semantics.
>
> In particular, I'm still trying to understand  stack vs GC-managed
> arrays, and slices.
>
> Finally, I have an associative array, and I want to pass it into a
> function. The function is only reading data. Would putting ref on in
> function parameter pass it by reference?

Ok two questions here:
1) What constitutes value vs reference passing
2) Allocation location

So basically you have two "locations" where something can be stored, on 
the stack or the heap.
Now I put it in quotes because they are both in RAM somewhere so it 
doesn't matter too much. The only difference is only a subset of the 
stack is readily allocatable at any single function call.

So in regarding to what gets passed by value, well that is simple.
If it is a class, you're passing a few pointers as your reference.
All primal types including pointers are passed as values.

If you use ref, you turn a type into a pointer auto magically (a 
location in the stack most likely).

Just so you're aware, arrays are slices in D (excluding static arrays). 
They are simply a pointer + length.
So I suppose you can think of references and slices as a container of 
sorts for other values which get passed in.