Re: Is this a bug in while-let or do I missunderstand it?

[Alfred M. Szmidt]

   @defmac while-let spec then-forms...
   Like @code{when-let*}, but repeat until a binding in @var{spec} is
   @code{nil}.  The return value is always @code{nil}.

The "Like FOO" is confusing -- it is not like when-let*, when-let* is
also not like let*.  E.g., when spec is (binding value) or just
(value) (!?) -- which should be mentioned in the manual.

These foo-LET are are mixing up the condition being tested and the
binding, when there is no binding the form seems to be just a test as
if you'd pass it directly to WHEN (or whatever).  There should be some
example that SPEC is not at all like in LET, and that:

(when-let* ((result1 (do-computation))
            (        (do-more result1)))
  (do-something result1))

is something like (I guess?):

(let ((result1 (do-computation)))
  (when result1
    (when (do-more result1)
      (do-something result2))))

And these mentions of "Like LET*" should be removed entierly.

But this is a better, and a good start.

   @code{while-let} replaces a common pattern in which a binding is
   established outside the @{while}-loop, tested as part of the condition of
   @{while} and subsequently changed inside the loop using the same expression
   that it was originally bound to:

   @example
   (let ((result (do-computation)))
     (while result
       (do-stuff-with result)
       (setq result (do-computation))))
   @end example

   Using @code{while-let}, this can be written more succinctly as:

   @example
   (while-let ((result (do-computation)))
     (do-stuff-with result))
   @end example

   The binding of @code{result} is reestablished at every iteration, therefore
   setting the value of @code{result} inside the loop has no effect. In order
   to end the loop, @code{(do-computation)} should eventually return
   @code{nil}.

   This example uses a single binding for clarity, but obviously
   @code{while-let} can establish multiple bindings. The loop runs as long as
   all bindings are non-@code{nil}.
   @end defmac
   ```

   Am I mistaken or is `while-let` a bit like a do..until loop that some
   languages offer?


   -- 
   Joost Kremers
   Life has its moments