Will macros just be syntactic sugar? [EXAMPLE]

[Don Clugston]

Davidl wrote:
> Nice work!
> The compiler now is damned powerful :)
> 
> Though I still prefer less string operation in compile time,
Yes. I think that's the key improvement to make.

  any idea of
> improving the
> macro syntax I posted? You see, D is going to bring AST macro in future 
> releases. Let's
> discuss the syntax it will use?

To the user, we should eliminate the quotes, and the mixin().
My example was a bit specific. Let's consider lazy evaluation.

void logging(bool bLog, lazy char [] msg);

which shouldn't evaluate msg unless bLog is true.
With my method, it would be:

bool bActive=true;
mixin(logging(`bActive, getFromDatabase("db", "downtime", event)`));

Obviously, we want to get rid of the mixin() and the ``. But that's 
probably the only thing we need to do, outside of library code.
Once we get rid of the ``, we have the requirement that all macro 
arguments must be syntactically valid D code. This makes things like 
your := impossible.

Then we have:
macro logging(char [][] args)
{
   return `if (` ~ args[0].stringof ~ `) printf("%s", ` ~ 
args[1].stringof ~ `);`;
}

(macros always return a char [], which is mixed in).

But that will look pretty awful if you want to do more than a single 
function call. OTOH, if we just get rid of the ``, we lose the ability 
to make decisions at compile time.
What then??