Converting C/C++ Code to D (#define extern)

[Bill Baxter]

Serg Kovrov wrote:
> Hi exiquio, you wrote:

>>
>> #define MovePiece(pos,from,to) do {                 \
>>     PieceList(pos,to) = PieceList(pos,from);            \
>>     PrevPiece(pos,NextPiece(pos,to)) = to;      \
>>     NextPiece(pos,PrevPiece(pos,to)) = to;      \
>>   } while(0)
> 

> Although later is somewhat suspicious - how loop meant to break?. 
> Perhaps there is another macro called as function, that has a break 
> statement. You could investigate what exactly it should do and rewrite 
> it more clear.
> 

That's a C preprocessor trick so that a call to the macro can pretend to 
be a regular function call.  It allows you to introduce a local 
variable, or have an if-else or loop in the macro.  E.g.

#define MaybeDoIt(cond) if (cond) \
    { int ret; \
      ret = prepareToDoIt(); \
      doIt(); \
    }

If you write it like that you can't call it like "MaybeDoIt(false);". 
The ';' on the end is syntactically incorrect.  Many C/C++ compilers 
would barf on it.  So you wrap it in a do while which needs a ';' at the 
end:
#define MaybeDoIt(cond) do{\
    if (cond) \
    { int ret; \
      ret = prepareToDoIt(); \
      doIt(); \
    } \
    while(0)

In this case it's really not necessary, though.  No loops, if-elses, or 
local variables are introduced so it could just be:

  #define MovePiece(pos,from,to)                \
      PieceList(pos,to) = PieceList(pos,from);  \
      PrevPiece(pos,NextPiece(pos,to)) = to;    \
      NextPiece(pos,PrevPiece(pos,to)) = to

Then you would call it like "MovePiece(a,b,c);" from your code.

Either way this should just be made into a regular function.  (Which D 
will inline if it feels like it).

--bb