Arc Forumnew | comments | leaders | submitlogin
2 points by CatDancer 5461 days ago | link | parent

> But if it's a macro, it seems to behave "like I want". Or is my example not good?

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

Try

  ((lambda () (fm)))
you can see that only if (fm) is invoked directly from the top level will the macro expansion be avoided.

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


1 point by palsecam 5461 days ago | link

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

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!

Thanks a lot CatDancer!

-----