Re: Why is there no `until' in elisp?

[Stefan Monnier <monnier@iro.umontreal.ca>]

> think `until' should refer to the version I gave because this is
> probably the one which is going to be implemented naively by most
> people,

BTW, this is only true if those people have to implement it on top of
the pre-existing `while`.  Once you go down to implementing it as
a sequence of byte-codes, then the `until` you proposed is no simpler
than the one I proposed.

So reversing your argument, if Elisp had my `until` and you wanted to
define `while` would you define it to return nil or to return t?
IOW would you define it as

    (defmacro while (test &rest body)
      `(until (not ,test) ,@body))
or
    (defmacro while (test &rest body)
      `(progn (until (not ,test) ,@body) nil))

?


        Stefan