But NO!

   cl> (defmacro m () (print "evaluated!"))
   M
   cl> (setf x 2)
   2
   cl> (if x t (m))
   T
   cl> (defun test-m (use-mac?) (if use-mac? (m) nil))
   "evaluated!"     <--- hmmm...
   TEST-M
   cl> (test-m t)
   "evaluated!"
   cl> (test-m nil)
   NIL              <--- ...no it's OK! (no "evaluated!")

The (print "evaluated!") itself evaluates to "evaluated!", so here

  cl> (test-m t)
    "evaluated!"

  (defmacro m ()
    (print "evaluated!")
    42)

However, I don't understand what you want to demonstrate with your macros.

   cl> (defmacro m () (print "evaluated!") 42)
   M
   cl> (if t (m) 43)
   "evaluated"
   42
   cl> (if nil (m) 43)
   43

   cl> (test-m t)
   42    

  cl> (test-m t)
  42

The behavior of 'if at the REPL is interesting, perhaps it is to support conditional compilation? However it is a special case, since only at the REPL would we be able to evaluate the test argument to the 'if before compiling the then or else forms. Doing so little as wrapping the 'if statement in a lambda causes the macro to be expanded regardless of the test argument:

  > ((lambda () (if t 3 (m))))
  "evaluated!"
  3

So the 'each of my dreams will be very difficult to have :-D! Maybe with lazy evaluation/JIT compilation [hmmm maybe not needed, see edit below].

Thanks for everything CatDancer!

EDIT:

Lol this stuff has no end. CatDancer I really enjoy all this, but it is late here and I will have to go to bed, seriously!

OK, so no REPL.

In if.lisp:

   (defmacro m () (print "Hello via mac!") 42)

   (defmacro fm ()  ; remember, myeach would also be a macro...
     `(if (eq (read) 'CALLMAC)
        (m) 
        (print "Hello via func")))

   (fm)

   paul@polo-laptop:~ $ echo 'CALLMAC' | sbcl --script if.lisp
   "Hello via mac!" 
   paul@polo-laptop:~ $ echo 'no call' | sbcl --script if.lisp
   "Hello via func"

   paul@polo-laptop:~ $ echo 'no call' | sbcl --script if.lisp
   "Hello via mac!" 
   "Hello via func"

"Only at the top level would we be able to evaluate the test argument to the 'if before compiling the then or else forms".

> So the 'each of my dreams will be very difficult to have

Well you know, the Arc compiler knows whether a variable is in the lexical scope. So you could implement your myeach in ac.scm, not using macros, but instead compiling to Scheme.

Or... how about...

  (mac ech args `(each _ ,@args))

But here; OK, if 'fm is a function, the behaviour is "like in Arc". But if it's a macro, it seems to behave "like I want". Or is my example not good? (Sorry I'm really tired here, I can't even realize this :-D).

I mean, don't you think 'myeach as a CL macro would work?

> (mac ech args `(each _ ,@args))

Actually I'm currently using that. I'm just using the name 'each_ instead and define it using the macro currying stuff of twilightsentry (see id=10139, very interesting).

   arc> (= each_ (>_ each '_))

Shall I wait until tomorrow to reply so that you can get some sleep? :)

Try

  ((lambda () (fm)))

> I mean, don't you think 'myeach as a CL macro would work?

What you need, in CL or in Arc, is a way to tell if a variable is defined at macro expansion time. Suppose Arc could tell you at macro expansion time if a variable was defined. Then you could say

  (def myeach (first . args)
    (if (defined first)
      `(each _ ,first ,@args)
      `(each ,first ,@args)))

Lol, yes I definitely go to bed now :-)

> ((lambda () (fm))

Nice demonstration indeed.

> What you need, in CL or in Arc, is a way to tell if a variable is defined at macro expansion time.

Right. I may try to modify Arc in this purpose one of these days.

> no magic needed in 'if, in either language :)

Magic definitely sucks :-D!

You are right to refuse "magic".

For Arc, oh this is way too much difficult for me, but if I had to try to solve the problem, I think I'd try to add a level of abstraction between the Scheme runtime and the Arc one (?!) Macros currently, as you know, directly run in the Scheme environment (am I all right?). I'd try to avoid that, and have more control over them by "compiling" them to a special form (`ar-macall') but not directly execute them (?!) And so 'if could then have a "higher priority" than macro expansion (?!)