freenode/#lisp - IRC Chatlog

5:10:51 Ekho- ** NICK Ekho

6:03:04 smokeink setting file position on a stream of type SB-INT:FORM-TRACKING-STREAM i.e. by doing: (file-position stream 50) give this error: "#<SB-INT:FORM-TRACKING-STREAM for ... {DC08F051}> is not positionable" what's the proper way to set the position for such a stream, or is it impossible?

6:03:13 smokeink *gives

6:04:49 smokeink I have some reader macros which set the position back into the stream, depending on the form they encounter when (read)ing

6:07:12 smokeink they work fine, but sbcl's (load ) fails with that error when reading forms with such dispatching macro characters, because it uses SB-INT:FORM-TRACKING-STREAM instead of a normal stream

6:12:43 beach Good morning everyone!

6:15:09 smokeink good morning!

6:46:28 smokeink I'll try repeated calls to (unread-char ) instead of (file-position ); it should work

7:12:17 emaczen https://plaster.tymoon.eu/view/1646#1648 -- can anyone help with passing C structs via libffi via sb-alien?

7:55:30 pjb smokeink: not conforming.

7:55:43 pjb smokeink: you can only call unread-char once after having read-char.

7:55:54 pjb smokeink: it's undefined what happens if you call it more.

7:56:26 pjb smokeink: "should" => go read clhs!

7:56:29 pjb clhs unread-char

7:56:29 specbot http://www.lispworks.com/reference/HyperSpec/Body/f_unrd_c.htm

7:57:02 pjb smokeink: file-position only works on file-streams. That's why it's called FILE-position, and not STREAM-position or something…

7:57:14 pjb smokeink: you can load from non-file-streams.

7:57:55 pjb smokeink: therefore your macro, to be able to "read" back, can only do it if it has saved the input in case of a non-file-stream.

7:58:07 aeth I suppose if you need to unread e.g. three times, you could write your own buffer for read/unread. As in, even if the character is no longer in the stream, it can be in *your* buffer.

7:58:47 aeth You could even use trivial-gray-streams if you wanted to do this using your own stream

8:02:00 pjb aeth: exactly. Have a look at the COM.INFORMATIMAGO.COMMON-LISP.CESARUM.PEEK-STREAM package.

8:02:12 pjb Or indeed, you could wrap it in a gray-streams.

9:14:18 smokeink aeth, pjb: thank you