Re: inline function

[Barbara Morris <bmorris@xxxxxxxxxx>]

On 2011/2/1 12:08 PM, Aaron Albertson wrote:
> ... here's something similar you can
> do in RPG (formatting is off, but you get the idea):
>
>   D container_t ds qualified template
>   D i 10i 0
>   D j 10i 0
>   D container ds likeds(container_t)
>   D offsets ds likeds(container_t)
>   D pNode s *
>   D pContainer s *
>   /free
>   pNode = %addr(container.j);
>   pContainer = pNode - (%addr(offsets.j) - %addr(offsets));

Earlier today, I hadn't looked carefully enough for the README that 
Mihael pointed to.  I was puzzled over how such a macro would be used, 
since the names of the structure and the structure member would have to 
be known at compile time.

Here's the sample function from the README:
  int my_cmp(const struct avltree_node *a,
             const struct avltree_node *b)
  {
     struct my_struct *p = avltree_container_of(a, my_struct, node);
     struct my_struct *q = avltree_container_of(b, my_struct, node);

     return p->key - q->key;
  }

Here's an equivalent function in RPG (unformatted and untested).  I 
marked the extra code needed to handle the C macro with ***, and the 
code that replaces the macro with "mac".

     P my_cmp             b
     D my_cmp             pi
     D   a                              *   value
     D   b                              *   value

     D p                  ds                likeds(my_struct_t)
     D                                      based(p_ptr)
     D q                  ds                likeds(my_struct_t)
     D                                      based(q_ptr)

***  D offsets            ds                likeds(my_struct_t)
***  D nodeOffset         s           10i 0
      /free
***       nodeOffset = %addr(offsets.node) - %addr(offsets);
mac       p_ptr = a - nodeOffset;
mac       q_ptr = b - nodeOffset;

          return p.key - q.key;
      /end-free
     P                    e