Re: Synonym Streams

Alan Bawden <alan@csail.mit.edu> writes:

I no longer remember why we designed this whole synonym stream thing.

[ ... ]

bivalent streams are useful.

 "In addition, SBCL supports various extensions of ANSI Common Lisp
streams:

*Bivalent Streams*
     A type of stream that can read and write both ‘character’ and
     ‘(unsigned-byte 8)’ values.

I'm not aware of any modern system where I/O has this feature.

POSIX man dup

I would be interested to know of any place that _does_ use synonym

I use the following for type 1 font dissasembler. I do not have the code
right now, but bivalent streams make it much easier to
read-char/read-byte.

;;
;;; Macros

(defmacro with-open-file-stream (direction type options &body body)
  `(with-open-file
       (,@options :direction ,direction :element-type ,type)
     ,@body))

(defmacro with-binary-input-stream (options &body forms)
  `(with-open-file-stream :input '(unsigned-byte 8) ,options ,@forms))

(defmacro with-ascii-input-stream (options &body forms)
  `(with-open-file-stream :input 'character ,options ,@forms))

(defmacro with-ascii-output-stream (options &body forms)
  `(with-open-file-stream :output 'character ,options ,@forms))

(defmacro with-binary-output-stream (options &body forms)
  `(with-open-file-stream :output '(unsigned-byte 8) ,options ,@forms))

streams to solve some real problem.

i do not have real problems.

- Alan

steve