Thanks Steve - that allows it to work.
Although the description for 'ido-mode is "Toggle ido speed-ups on or
off..."

So maybe if I waited a year or two ("speed-ups" must be off by default) then
I would have eventually received the correct prompt/behaviour? :-)

Obviously invoking ido-mode has some undescribed side-effect that allows the
completing-read to  work. Hopefully somebody will either fix this problem or
put in a description in ido-completing-read that you have to turn on
speed-ups first!

Thanks greatly - I can now get my original defun working! :-)

Peter

On Wed, Jun 24, 2009 at 5:08 PM, Stephen Berman <stephen.berman@gmx.net>wrote:

> On Wed, 24 Jun 2009 07:37:42 +1000 Peter Milliken <
> peter.milliken@gmail.com> wrote:
>
> > This bug is also present in Emacs 22.3. I am attempting to use
> > ido-completing-read in a defun and the function "hangs" at the prompt
> > i.e. it does no completion at all, it will not allow me to cancel the
> > command, or accept a string typed in followed by RET.
> >
> > I have produced a small test function to attempt to minimise possible
> > problems on my part:
> >
> > (defun test ()
> >   (interactive)
> >   (let ((a)(d))
> >     (setq d '("abc" "xyz" "abe" "def"))
> >     (setq a (ido-completing-read "prompt: " d))))
> >
> > My *understanding* of reading the defun documentation is that I should
> > be able to type "a<TAB>" (at the prompt) and have a completion list of
> > "abc" and "abe" offered. But this does not happen, all I get is "a
> > TAB". If I hit C-g nothing happens, the prompt line remains at the
> > command line.
>
> I get this behavior as well (with GNU Emacs 23.1.50.1
> (i686-pc-linux-gnu, GTK+ Version 2.14.4) of 2009-06-23 on escher).
> However, if I add `(ido-mode 1)' before the first setq, then it works as
> I assume it's supposed to: typing `M-x test' shows "prompt: {abc | xyz |
> abe | def}" in the minibuffer, and then typing `a' (without subsequent
> TAB) shows "prompt: a[b] {abc | abe}", and `C-g' quits the minibuffer.
>
> Steve Berman
>