On Sat, Mar 24, 2018 at 7:14 PM, Robert Dodier <robert.dodier@gmail.com> wrote:

Hi,

I'm wondering if there is a way to get the list of allowable values of
the :EXTERNAL-FORMAT keyword for OPEN. Is there a way to determine the
possible values at run time? I looked into the source code for
MAKE-FILE-STREAM but I got a little lost ... perhaps someone can point
me in the right direction.

What I'm trying to do is to verify whether a given format is
acceptable. I am thinking that I can inspect a list to see if the
given format is on the list. Another workable solution would be a
function which can report whether the given format is acceptable, if
such a function exists.

I don't know that there's a way to enumerate them. However you can call open with an external format and it seems it will throw an exception if it isn't one.

Undefined encoding: FUDGE

[Condition of type simple-error]

Restarts:

0: [retry] Retry SLIME REPL evaluation request.

1: [*abort] Return to SLIME's top level.

2: [abort] Abort thread.

Backtrace:

0: (invoke-debugger #<simple-error {2EDCBCEA}>)

1: org.armedbear.lisp.Lisp.error(Lisp.java:382)

There's also some documentation in FileStream.java that shows that one of the possibilities is a list with a charset as car. You can get the available charsets with

(loop for k being the hash-keys of (jss::hashmap-to-hashtable (#"availableCharsets" 'charset.charset)) collect k)

Alan

Thanks for your help,

Robert Dodier