Rant about Gray streams

gray-streams-rant.txt

   The Gray streams interface mirrors the ordinary streams interface
   almost without change.  This creates many issues: for example, if
   one wants to define, say, a decompressing stream, which operates in
   terms of octets, but also make it usable as a character stream, one
   is left to implement character decoding by himself.  Franz's
   SIMPLE-STREAMS details more such issues.

   For a while I've felt dissatisfied with Common Lisp streams.  I
   think it's because of the Gray streams interface, which are not
   part of Common Lisp proper.

   SBCL has an SB-SIMPLE-STREAMS contrib module, but it appears unused
   because when I tried an example from Franz's documentation (the
   WHIZ-BANG stream) it failed to work.  I've fixed the bug and now it
   seems to work again, but how many more bugs lurk there?

   Franz's documentation is also lacking.  I suppose it's because they
   rely on the user to learn from the examples provided with Allegro
   Common Lisp, but I am not an Allegro user.  Thus, the next time I
   want to implement a stream, it will happen with the help of the
   contrib module's source code.

   The final straw that led me to have such strong opinions about Gray
   streams came from trying to use a GZIP decompressing stream as a
   character stream for parsing GZIP-compressed XML.  The
   "gzip-stream" library, which uses Gray streams, has a
   STREAM-READ-CHAR method that uses CODE-CHAR, and disregards the
   stream type in STREAM-READ-SEQUENCE, always returning octet
   vectors.  Therefore it failed to parse.  The "chipz" library, also
   using Gray streams, doesn't even bother with character streams.

   If these libraries were to use SIMPLE-STREAMS, they would only need
   to implement the binary stream handling, and character translation
   would be provided automatically.

   I think Gray streams is a good example of how conflating two
   different user types into a single (well, almost) interface can
   create problems.  Both stream users and stream definers deserve a
   simple interface to help them perform their task.  In the case of
   Gray streams, which parrots the stream user interface, complexity
   is created for the stream definer.

   Before my GZIP drama I thought that the Gray streams interface
   weird for mirroring the Common Lisp interface, and that it was
   incomplete (no STREAM-FILE-LENGTH), and that it was annoying to
   have duplication in implementing STREAM-READ-CHAR,
   STREAM-READ-SEQUENCE, STREAM-READ-BYTE, but I didn't realize how
   deeply it contributed to my dissatisfaction with Common Lisp
   streams, and I didn't seriously think about an alternative
   interface.  Now that I've looked into SIMPLE-STREAMS, I feel better
   about Common Lisp streams, and I feel like I need to bring myself
   to think about alternative interfaces more.