On 09/04/2014 02:54 AM, nikki wrote:
> a pointer variable to save an adres of a function, then dereferencing
to use
> it.
If possible, even in C, I would recommend using a 'function pointer' for
that. However, there are cases where the signature of the function
should be unknown to the code that is storing it so a void* is used.
(Note that, as discussed on these forums in the past, void* has always
been intended to be a data pointer. The fact that it works for function
pointers is something we get as lucky accidents, which will most
probably always supported by compilers and CPUs.)
Here is how D does function pointers:
http://dlang.org/expression.html#FunctionLiteral
And a chapter that expands on those:
http://ddili.org/ders/d.en/lambda.html
> Now I am wondering when to use the ** ?
The simple answer is when dealing with the address of a type that is
'void*' itself. In other words, there is nothing special about **: It
appears as the type that is "a pointer to a pointer". Inserting spaces:
int * p; // A pointer to an int
void* * q; // A pointer to a void*
// (untested)
static assert (is (typeof(*p) == int));
static assert (is (typeof(*q) == void*));
int i;
*p = i; // Can store an int
void* v;
*q = v; // Can store a void*
Ali
