guile/NEWS

Guile NEWS --- history of user-visible changes.  2 Aug 1996  -*- text -*-
Copyright (C) 1996 Free Software Foundation, Inc.
See the end for copying conditions.

Please send Guile bug reports to bug-guile@prep.ai.mit.edu.

Guile 1.0b3

Changes since Thursday, September 5:


* Guile now distinguishes between #f and the empty list.

This is for compatibility with the IEEE standard, the (possibly)
upcoming Revised^5 Report on Scheme, and many extant Scheme
implementations.

Guile used to have #f and '() denote the same object, to make Scheme's
type system more compatible with Emacs Lisp's.  However, the change
caused too much trouble for Scheme programmers, and we found another
way to reconcile Emacs Lisp with Scheme that didn't require this.


* You can now use Guile as a shell script interpreter.

To paraphrase the SCSH manual:

    When Unix tries to execute an executable file whose first two
    characters are the `#!', it treats the file not as machine code to
    be directly executed by the native processor, but as source code
    to be executed by some interpreter.  The interpreter to use is
    specified immediately after the #! sequence on the first line of
    the source file.  The kernel reads in the name of the interpreter,
    and executes that instead.  It passes the interpreter the source
    filename as its first argument, with the original arguments
    following.  Consult the Unix man page for the `exec' system call
    for more information.

Guile now recognizes a '-s' command line switch, whose argument is the
name of a file of Scheme code to load.  It also treats the two
characters `#!' as the start of a comment, terminated by `!#'.  Thus,
to make a file of Scheme code directly executable by Unix, insert the
following two lines at the top of the file:

#!/usr/local/bin/guile -s
!#

Guile treats the argument of the `-s' command-line switch as the name
of a file of Scheme code to load, and treats the sequence `#!' as the
start of a block comment, terminated by `!#'.

For example, here's a version of 'echo' written in Scheme:

#!/usr/local/bin/guile -s
!#
(let loop ((args (cdr (program-arguments))))
  (if (pair? args)
      (begin
	(display (car args))
	(if (pair? (cdr args))
	    (display " "))
	(loop (cdr args)))))
(newline)

Why does `#!' start a block comment terminated by `!#', instead of the
end of the line?  That is the notation SCSH uses, and although we
don't yet support the other SCSH features that motivate that choice,
we would like to be backward-compatible with any existing Guile
scripts once we do.

Note that some very old Unix systems don't support the `#!' syntax.


* You can now run Guile without installing it.

Previous versions of the interactive Guile interpreter (`guile')
couldn't start up unless Guile's Scheme library had been installed;
they used the value of the environment variable `SCHEME_LOAD_PATH'
later on in the startup process, but not to find the startup code
itself.  Now Guile uses `SCHEME_LOAD_PATH' in all searches for Scheme
code.

To run Guile without installing it, build it in the normal way, and
then set the environment variable `SCHEME_LOAD_PATH' to a
colon-separated list of directories, including the top-level directory
of the Guile sources.  For example, if you unpacked Guile so that the
full filename of this NEWS file is /home/jimb/guile-1.0b3/NEWS, then
you might say

	export SCHEME_LOAD_PATH=/home/jimb/my-scheme:/home/jimb/guile-1.0b3

* Guile's header files should no longer conflict with your system's
header files.

In order to compile code which #included <libguile.h>, previous
versions of Guile required you to add a directory containing all the
Guile header files to your #include path.  This was a problem, since
Guile's header files have names which conflict with many systems'
header files.

Now only <libguile.h> need appear in your #include path; you must
refer to all Guile's other header files as <libguile/mumble.h>.
Guile's installation procedure puts libguile.h in $(includedir), and
the rest in $(includedir)/libguile.

* The compiled-library-path function has been deleted from libguile.

* A variable and two new functions have been added to libguile:

** The variable %load-path now tells Guile which directories to search
for Scheme code.  Its value is a list of strings, each of which names
a directory.

** (%search-load-path FILENAME) searches the directories listed in the
value of the %load-path variable for a Scheme file named FILENAME.  If
it finds a match, then it returns its full filename.  Otherwise, it
returns #f.  %search-load-path will not return matches that refer to
directories.

** (%try-load-path FILENAME :optional CASE-INSENSITIVE-P SHARP)
searches the directories listed in %load-path for a file named
FILENAME, and loads it if it finds it.  If it can't read FILENAME for
any reason, it throws an error.

The arguments CASE-INSENSITIVE-P and SHARP are interpreted as by the
%try-load function.



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Copyright (C) 1996 Free Software Foundation, Inc.

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