FunctionPackage: exclToCDocOverviewCGDocRelNotesFAQIndexPermutedIndex
Allegro CL version 9.0
This page is new in 9.0.


Arguments: stream

This function is similar to unread-char, but it backs up to the previous octet rather than character. It is also similar in that if unread-byte is called immediately after a "back-up" function (i.e. peek-char/peek-byte or unread-char/unread-byte) it may fail. However, it need not fail; if the stream being operated on is not currently positioned at the beginning of its buffer, even after a backup function has just been called, then unread-byte may still succeed. There is currently no portable way to know whether an unread-byte will work, unless the last operation on the stream was a read operation other than a back-up function.

unread-byte currently does not work on Gray streams - error is called when unread-byte is called on a Gray stream. (Gray streams are discussed in gray-streams.htm.)

See peek-byte and unread-byte in streams.htm for a general discussion of this function and the related peek-byte.

Copyright (c) 1998-2012, Franz Inc. Oakland, CA., USA. All rights reserved.
Documentation for Allegro CL version 9.0. This page is new in the 9.0 release.
Created 2010.1.21.

Allegro CL version 9.0
This page is new in 9.0.