Question

I’m trying to use D’s equivalent of function pointer as a way of specifying optional functions as one field in a struct, of which I’m initializing an array of. This would be simple in C (aside from the messy syntax) but I’m stuck. This program:

struct Foo {
    ubyte code;
    bool yup;
    void function(ubyte[] data,  int size) special;
} 

void boof(ubyte[] data, int size)   {
    /*do something*/
}

static immutable Foo[] markdefs = [
  {0xF2,  true,   null},
  {0xE4,  true,   boof},
  {0xEE,  false,  null}
];

void main()  {
}

gives me these errors:

funptr.d(17): Error: function funptr.boof (ubyte[] data, int size) is not 
callable using  argument types ()
funptr.d(17): Error: expected 2 function arguments, not 0
funptr.d(17):        called from here: boof()
funptr.d(17): Error: cannot implicitly convert expression (boof()) of type 
void to void function(ubyte[] data, int size)

I’m using dmd for D2 on a 64-bit Linux machine.

Answer 1

On line 17, your use of boof is a function call with no parameters (D allows the absence of parens). What you want is to take the reference of boof with the & operator.