[Audacity-nyquist] "FORMAT T" vs. "FORMAT NIL" in Audacity Nyquist plugins

[edgar <edg...@we...>]

Edgar wrote:

 > format t "string")
 >
 > has the same effect as:
 >
 > (princ (format nil "string"))
 >
 > format t = print to stdout, return NIL
 > format nil = print nothing, instead return the string

Steve wrote:

 > When I use (format t "string") I only see the output in the debug
 > window, (Audacity shows the message "Nyquist did not return audio")
 > whereas using (princ (format nil "string")) outputs the string as
 > a pop-up message.
 >
 > I assumed that that was supposed to happen?

Now I understand what you mean. :-)

There is once again a weirdness in the Audacity Nyquist interface
(David Sky asked me this at least ten times):

If a plugin returns a string instead of a sound, the string gets
displayed in the popup window instead of the "Nyquist did not
return audio" message.

So if the last line in the plugin is:

(format nil "string")

then the FORMAT return-value (the string) gets displayed in the
popup window, but not in the Debug window (you do not necessarily
need the PRINC function for that, it also works without PRINC).

While with:

(format t "string")

at any place in the Nyquist code the string gets displayed in the
Debug window. If "format t" is the last line in the plugin code
then "Nyquist did not return audio" will get displayed in the
popup window because in this case the FORMAT return-value is NIL
and NIL is not a string.

See also the explanation of the different Nyquist return values:

http://www.audacity-forum.de/download/edgar/nyquist/nyquist-doc/devel/audacity-nyquist-en.htm#return

If you want a string displayed in both, the popup window as well
as in the Debug window there is no other way than to write:

(format t "string")
(format nil "string")

The order is important: "format t" must come first, because it
returns NIL, only "format nil" returns a string.

- edgar





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