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[bpt/guile.git] / NEWS

Guile NEWS --- history of user-visible changes.  -*- text -*-
Copyright (C) 1996, 1997 Free Software Foundation, Inc.
See the end for copying conditions.

Please send Guile bug reports to bug-guile@prep.ai.mit.edu.
\f
Changes in Guile 1.2:

[[trim out any sections we don't need]]

* Changes to the distribution

* Changes to the procedure for linking libguile with your programs

* Changes to Scheme functions and syntax

** Guile now supports a new R4RS-compliant syntax for keywords.  A
token of the form #:NAME, where NAME has the same syntax as a Scheme
symbol, is the external representation of the keyword named NAME.
Keyword objects print using this syntax as well, so values containing
keyword objects can be read back into Guile.  When used in an
expression, keywords are self-quoting objects.

Guile suports this read syntax, and uses this print syntax, regardless
of the current setting of the `keyword' read option.  The `keyword'
read option only controls whether Guile recognizes the `:NAME' syntax,
which is incompatible with R4RS.  (R4RS says such token represent
symbols.)

** Guile has regular expression support again.  Guile 1.0 included
functions for matching regular expressions, based on the Rx library.
In Guile 1.1, the Guile/Rx interface was removed to simplify the
distribution, and thus Guile had no regular expression support.  Guile
1.2 now adds back the most commonly used functions, and supports all
of SCSH's regular expression functions.  They are:

*** [[get docs from Tim?]]

* Changes to the gh_ interface

* Changes to the scm_ interface

\f
Changes in Guile 1.1 (Fri May 16 1997):

* Changes to the distribution.

The Guile 1.0 distribution has been split up into several smaller
pieces:
guile-core --- the Guile interpreter itself.
guile-tcltk --- the interface between the Guile interpreter and
        Tcl/Tk; Tcl is an interpreter for a stringy language, and Tk
        is a toolkit for building graphical user interfaces.
guile-rgx-ctax --- the interface between Guile and the Rx regular
        expression matcher, and the translator for the Ctax
        programming language.  These are packaged together because the
        Ctax translator uses Rx to parse Ctax source code.

This NEWS file describes the changes made to guile-core since the 1.0
release.

We no longer distribute the documentation, since it was either out of
date, or incomplete.  As soon as we have current documentation, we
will distribute it.

* Changes to the stand-alone interpreter

** guile now accepts command-line arguments compatible with SCSH, Olin
Shivers' Scheme Shell.

In general, arguments are evaluated from left to right, but there are
exceptions.  The following switches stop argument processing, and
stash all remaining command-line arguments as the value returned by
the (command-line) function.
  -s SCRIPT      load Scheme source code from FILE, and exit
  -c EXPR        evalute Scheme expression EXPR, and exit
  --             stop scanning arguments; run interactively

The switches below are processed as they are encountered.
  -l FILE        load Scheme source code from FILE
  -e FUNCTION    after reading script, apply FUNCTION to
                 command line arguments
  -ds            do -s script at this point
  --emacs        enable Emacs protocol (experimental)
  -h, --help     display this help and exit
  -v, --version  display version information and exit
  \              read arguments from following script lines

So, for example, here is a Guile script named `ekko' (thanks, Olin)
which re-implements the traditional "echo" command:

#!/usr/local/bin/guile -s
!#
(define (main args)
        (map (lambda (arg) (display arg) (display " "))
             (cdr args))
        (newline))

(main (command-line))

Suppose we invoke this script as follows:

        ekko a speckled gecko

Through the magic of Unix script processing (triggered by the `#!'
token at the top of the file), /usr/local/bin/guile receives the
following list of command-line arguments:

        ("-s" "./ekko" "a" "speckled" "gecko")

Unix inserts the name of the script after the argument specified on
the first line of the file (in this case, "-s"), and then follows that
with the arguments given to the script.  Guile loads the script, which
defines the `main' function, and then applies it to the list of
remaining command-line arguments, ("a" "speckled" "gecko").

In Unix, the first line of a script file must take the following form:

#!INTERPRETER ARGUMENT

where INTERPRETER is the absolute filename of the interpreter
executable, and ARGUMENT is a single command-line argument to pass to
the interpreter.

You may only pass one argument to the interpreter, and its length is
limited.  These restrictions can be annoying to work around, so Guile
provides a general mechanism (borrowed from, and compatible with,
SCSH) for circumventing them.

If the ARGUMENT in a Guile script is a single backslash character,
`\', Guile will open the script file, parse arguments from its second
and subsequent lines, and replace the `\' with them.  So, for example,
here is another implementation of the `ekko' script:

#!/usr/local/bin/guile \
-e main -s
!#
(define (main args)
  (for-each (lambda (arg) (display arg) (display " "))
            (cdr args))
  (newline))

If the user invokes this script as follows:

        ekko a speckled gecko

Unix expands this into

        /usr/local/bin/guile \ ekko a speckled gecko

When Guile sees the `\' argument, it replaces it with the arguments
read from the second line of the script, producing:

        /usr/local/bin/guile -e main -s ekko a speckled gecko

This tells Guile to load the `ekko' script, and apply the function
`main' to the argument list ("a" "speckled" "gecko").

Here is how Guile parses the command-line arguments:
- Each space character terminates an argument.  This means that two
  spaces in a row introduce an empty-string argument.
- The tab character is not permitted (unless you quote it with the
  backslash character, as described below), to avoid confusion.
- The newline character terminates the sequence of arguments, and will
  also terminate a final non-empty argument.  (However, a newline
  following a space will not introduce a final empty-string argument;
  it only terminates the argument list.)
- The backslash character is the escape character.  It escapes
  backslash, space, tab, and newline.  The ANSI C escape sequences
  like \n and \t are also supported.  These produce argument
  constituents; the two-character combination \n doesn't act like a
  terminating newline.  The escape sequence \NNN for exactly three
  octal digits reads as the character whose ASCII code is NNN.  As
  above, characters produced this way are argument constituents.
  Backslash followed by other characters is not allowed.

* Changes to the procedure for linking libguile with your programs

** Guile now builds and installs a shared guile library, if your
system support shared libraries.  (It still builds a static library on
all systems.)  Guile automatically detects whether your system
supports shared libraries.  To prevent Guile from buildisg shared
libraries, pass the `--disable-shared' flag to the configure script.

Guile takes longer to compile when it builds shared libraries, because
it must compile every file twice --- once to produce position-
independent object code, and once to produce normal object code.

** The libthreads library has been merged into libguile.

To link a program against Guile, you now need only link against
-lguile and -lqt; -lthreads is no longer needed.  If you are using
autoconf to generate configuration scripts for your application, the
following lines should suffice to add the appropriate libraries to
your link command:

### Find quickthreads and libguile.
AC_CHECK_LIB(qt, main)
AC_CHECK_LIB(guile, scm_shell)

* Changes to Scheme functions

** Guile Scheme's special syntax for keyword objects is now optional,
and disabled by default.

The syntax variation from R4RS made it difficult to port some
interesting packages to Guile.  The routines which accepted keyword
arguments (mostly in the module system) have been modified to also
accept symbols whose names begin with `:'.

To change the keyword syntax, you must first import the (ice-9 debug)
module:
        (use-modules (ice-9 debug))

Then you can enable the keyword syntax as follows:
        (read-set! keywords 'prefix)

To disable keyword syntax, do this:
        (read-set! keywords #f)

** Many more primitive functions accept shared substrings as
arguments.  In the past, these functions required normal, mutable
strings as arguments, although they never made use of this
restriction.

** The uniform array functions now operate on byte vectors.  These
functions are `array-fill!', `serial-array-copy!', `array-copy!',
`serial-array-map', `array-map', `array-for-each', and
`array-index-map!'.

** The new functions `trace' and `untrace' implement simple debugging
support for Scheme functions.

The `trace' function accepts any number of procedures as arguments,
and tells the Guile interpreter to display each procedure's name and
arguments each time the procedure is invoked.  When invoked with no
arguments, `trace' returns the list of procedures currently being
traced.

The `untrace' function accepts any number of procedures as arguments,
and tells the Guile interpreter not to trace them any more.  When
invoked with no arguments, `untrace' untraces all curretly traced
procedures.

The tracing in Guile has an advantage over most other systems: we
don't create new procedure objects, but mark the procedure objects
themselves.  This means that anonymous and internal procedures can be
traced.

** The function `assert-repl-prompt' has been renamed to
`set-repl-prompt!'.  It takes one argument, PROMPT.
- If PROMPT is #f, the Guile read-eval-print loop will not prompt.
- If PROMPT is a string, we use it as a prompt.
- If PROMPT is a procedure accepting no arguments, we call it, and
  display the result as a prompt.
- Otherwise, we display "> ".

** The new function `eval-string' reads Scheme expressions from a
string and evaluates them, returning the value of the last expression
in the string.  If the string contains no expressions, it returns an
unspecified value.

** The new function `thunk?' returns true iff its argument is a
procedure of zero arguments.

** `defined?' is now a builtin function, instead of syntax.  This
means that its argument should be quoted.  It returns #t iff its
argument is bound in the current module.

** The new syntax `use-modules' allows you to add new modules to your
environment without re-typing a complete `define-module' form.  It
accepts any number of module names as arguments, and imports their
public bindings into the current module.

** The new function (module-defined? NAME MODULE) returns true iff
NAME, a symbol, is defined in MODULE, a module object.

** The new function `builtin-bindings' creates and returns a hash
table containing copies of all the root module's bindings.

** The new function `builtin-weak-bindings' does the same as
`builtin-bindings', but creates a doubly-weak hash table.

** The `equal?' function now considers variable objects to be
equivalent if they have the same name and the same value.

** The new function `command-line' returns the command-line arguments
given to Guile, as a list of strings.

When using guile as a script interpreter, `command-line' returns the
script's arguments; those processed by the interpreter (like `-s' or
`-c') are omitted.  (In other words, you get the normal, expected
behavior.)  Any application that uses scm_shell to process its
command-line arguments gets this behavior as well.

** The new function `load-user-init' looks for a file called `.guile'
in the user's home directory, and loads it if it exists.  This is
mostly for use by the code generated by scm_compile_shell_switches,
but we thought it might also be useful in other circumstances.

** The new function `log10' returns the base-10 logarithm of its
argument.

** Changes to I/O functions

*** The functions `read', `primitive-load', `read-and-eval!', and 
`primitive-load-path' no longer take optional arguments controlling
case insensitivity and a `#' parser.

Case sensitivity is now controlled by a read option called
`case-insensitive'.  The user can add new `#' syntaxes with the
`read-hash-extend' function (see below).

*** The new function `read-hash-extend' allows the user to change the
syntax of Guile Scheme in a somewhat controlled way.

(read-hash-extend CHAR PROC)
  When parsing S-expressions, if we read a `#' character followed by
  the character CHAR, use PROC to parse an object from the stream.
  If PROC is #f, remove any parsing procedure registered for CHAR.

  The reader applies PROC to two arguments: CHAR and an input port.

*** The new functions read-delimited and read-delimited! provide a 
general mechanism for doing delimited input on streams.

(read-delimited DELIMS [PORT HANDLE-DELIM])
  Read until we encounter one of the characters in DELIMS (a string),
  or end-of-file.  PORT is the input port to read from; it defaults to
  the current input port.  The HANDLE-DELIM parameter determines how
  the terminating character is handled; it should be one of the
  following symbols:

    'trim     omit delimiter from result
    'peek     leave delimiter character in input stream
    'concat   append delimiter character to returned value
    'split    return a pair: (RESULT . TERMINATOR)

  HANDLE-DELIM defaults to 'peek.

(read-delimited! DELIMS BUF [PORT HANDLE-DELIM START END])
  A side-effecting variant of `read-delimited'.

  The data is written into the string BUF at the indices in the
  half-open interval [START, END); the default interval is the whole
  string: START = 0 and END = (string-length BUF).  The values of
  START and END must specify a well-defined interval in BUF, i.e.
  0 <= START <= END <= (string-length BUF).

  It returns NBYTES, the number of bytes read.  If the buffer filled
  up without a delimiter character being found, it returns #f.  If the
  port is at EOF when the read starts, it returns the EOF object.

  If an integer is returned (i.e., the read is successfully terminated
  by reading a delimiter character), then the HANDLE-DELIM parameter
  determines how to handle the terminating character.  It is described
  above, and defaults to 'peek.

(The descriptions of these functions were borrowed from the SCSH
manual, by Olin Shivers and Brian Carlstrom.)

*** The `%read-delimited!' function is the primitive used to implement
`read-delimited' and `read-delimited!'.

(%read-delimited! DELIMS BUF GOBBLE? [PORT START END])

This returns a pair of values: (TERMINATOR . NUM-READ).
- TERMINATOR describes why the read was terminated.  If it is a
  character or the eof object, then that is the value that terminated
  the read.  If it is #f, the function filled the buffer without finding
  a delimiting character.
- NUM-READ is the number of characters read into BUF.

If the read is successfully terminated by reading a delimiter
character, then the gobble? parameter determines what to do with the
terminating character.  If true, the character is removed from the
input stream; if false, the character is left in the input stream
where a subsequent read operation will retrieve it.  In either case,
the character is also the first value returned by the procedure call.

(The descriptions of this function was borrowed from the SCSH manual,
by Olin Shivers and Brian Carlstrom.)

*** The `read-line' and `read-line!' functions have changed; they now
trim the terminator by default; previously they appended it to the
returned string.  For the old behavior, use (read-line PORT 'concat).

*** The functions `uniform-array-read!' and `uniform-array-write!' now
take new optional START and END arguments, specifying the region of
the array to read and write.

*** The `ungetc-char-ready?' function has been removed.  We feel it's
inappropriate for an interface to expose implementation details this
way.

** Changes to the Unix library and system call interface

*** The new fcntl function provides access to the Unix `fcntl' system
call.

(fcntl PORT COMMAND VALUE)
  Apply COMMAND to PORT's file descriptor, with VALUE as an argument.
  Values for COMMAND are:

    F_DUPFD     duplicate a file descriptor
    F_GETFD     read the descriptor's close-on-exec flag
    F_SETFD     set the descriptor's close-on-exec flag to VALUE
    F_GETFL     read the descriptor's flags, as set on open
    F_SETFL     set the descriptor's flags, as set on open to VALUE
    F_GETOWN    return the process ID of a socket's owner, for SIGIO
    F_SETOWN    set the process that owns a socket to VALUE, for SIGIO
    FD_CLOEXEC  not sure what this is

For details, see the documentation for the fcntl system call.

*** The arguments to `select' have changed, for compatibility with
SCSH.  The TIMEOUT parameter may now be non-integral, yielding the
expected behavior.  The MILLISECONDS parameter has been changed to
MICROSECONDS, to more closely resemble the underlying system call.
The RVEC, WVEC, and EVEC arguments can now be vectors; the type of the
corresponding return set will be the same.

*** The arguments to the `mknod' system call have changed.  They are
now:

(mknod PATH TYPE PERMS DEV)
  Create a new file (`node') in the file system.  PATH is the name of
  the file to create.  TYPE is the kind of file to create; it should
  be 'fifo, 'block-special, or 'char-special.  PERMS specifies the
  permission bits to give the newly created file.  If TYPE is
  'block-special or 'char-special, DEV specifies which device the
  special file refers to; its interpretation depends on the kind of
  special file being created.

*** The `fork' function has been renamed to `primitive-fork', to avoid
clashing with various SCSH forks.

*** The `recv' and `recvfrom' functions have been renamed to `recv!'
and `recvfrom!'.  They no longer accept a size for a second argument;
you must pass a string to hold the received value.  They no longer
return the buffer.  Instead, `recv' returns the length of the message
received, and `recvfrom' returns a pair containing the packet's length
and originating address. 

*** The file descriptor datatype has been removed, as have the
`read-fd', `write-fd', `close', `lseek', and `dup' functions.
We plan to replace these functions with a SCSH-compatible interface.

*** The `create' function has been removed; it's just a special case
of `open'.

*** There are new functions to break down process termination status
values.  In the descriptions below, STATUS is a value returned by
`waitpid'.

(status:exit-val STATUS)
  If the child process exited normally, this function returns the exit
  code for the child process (i.e., the value passed to exit, or
  returned from main).  If the child process did not exit normally,
  this function returns #f.

(status:stop-sig STATUS)
  If the child process was suspended by a signal, this function
  returns the signal that suspended the child.  Otherwise, it returns
  #f.

(status:term-sig STATUS)
  If the child process terminated abnormally, this function returns
  the signal that terminated the child.  Otherwise, this function
  returns false.

POSIX promises that exactly one of these functions will return true on
a valid STATUS value.

These functions are compatible with SCSH.

*** There are new accessors and setters for the broken-out time vectors
returned by `localtime', `gmtime', and that ilk.  They are:

  Component                 Accessor     Setter
  ========================= ============ ============
  seconds                   tm:sec       set-tm:sec
  minutes                   tm:min       set-tm:min
  hours                     tm:hour      set-tm:hour
  day of the month          tm:mday      set-tm:mday
  month                     tm:mon       set-tm:mon
  year                      tm:year      set-tm:year
  day of the week           tm:wday      set-tm:wday
  day in the year           tm:yday      set-tm:yday
  daylight saving time      tm:isdst     set-tm:isdst
  GMT offset, seconds       tm:gmtoff    set-tm:gmtoff
  name of time zone         tm:zone      set-tm:zone

*** There are new accessors for the vectors returned by `uname',
describing the host system:

  Component                                      Accessor
  ============================================== ================
  name of the operating system implementation    utsname:sysname
  network name of this machine                   utsname:nodename
  release level of the operating system          utsname:release
  version level of the operating system          utsname:version
  machine hardware platform                      utsname:machine

*** There are new accessors for the vectors returned by `getpw',
`getpwnam', `getpwuid', and `getpwent', describing entries from the
system's user database:

  Component              Accessor
  ====================== =================
  user name              passwd:name
  user password          passwd:passwd
  user id                passwd:uid
  group id               passwd:gid
  real name              passwd:gecos
  home directory         passwd:dir
  shell program          passwd:shell

*** There are new accessors for the vectors returned by `getgr',
`getgrnam', `getgrgid', and `getgrent', describing entries from the
system's group database:

  Component               Accessor
  ======================= ============
  group name              group:name
  group password          group:passwd
  group id                group:gid
  group members           group:mem

*** There are new accessors for the vectors returned by `gethost',
`gethostbyaddr', `gethostbyname', and `gethostent', describing
internet hosts:

  Component                 Accessor
  ========================= ===============
  official name of host     hostent:name
  alias list                hostent:aliases
  host address type         hostent:addrtype
  length of address         hostent:length
  list of addresses         hostent:addr-list

*** There are new accessors for the vectors returned by `getnet',
`getnetbyaddr', `getnetbyname', and `getnetent', describing internet
networks:

  Component                 Accessor
  ========================= ===============
  official name of net      netent:name
  alias list                netent:aliases
  net number type           netent:addrtype
  net number                netent:net

*** There are new accessors for the vectors returned by `getproto',
`getprotobyname', `getprotobynumber', and `getprotoent', describing
internet protocols:

  Component                 Accessor
  ========================= ===============
  official protocol name    protoent:name
  alias list                protoent:aliases
  protocol number           protoent:proto

*** There are new accessors for the vectors returned by `getserv',
`getservbyname', `getservbyport', and `getservent', describing
internet protocols:

  Component                 Accessor
  ========================= ===============
  official service name     servent:name   
  alias list                servent:aliases
  port number               servent:port   
  protocol to use           servent:proto  

*** There are new accessors for the sockaddr structures returned by
`accept', `getsockname', `getpeername', `recvfrom!':

  Component                                Accessor
  ======================================== ===============
  address format (`family')                sockaddr:fam 
  path, for file domain addresses          sockaddr:path
  address, for internet domain addresses   sockaddr:addr
  TCP or UDP port, for internet            sockaddr:port

*** The `getpwent', `getgrent', `gethostent', `getnetent',
`getprotoent', and `getservent' functions now return #f at the end of
the user database.  (They used to throw an exception.)

Note that calling MUMBLEent function is equivalent to calling the
corresponding MUMBLE function with no arguments.

*** The `setpwent', `setgrent', `sethostent', `setnetent',
`setprotoent', and `setservent' routines now take no arguments.

*** The `gethost', `getproto', `getnet', and `getserv' functions now
provide more useful information when they throw an exception.

*** The `lnaof' function has been renamed to `inet-lnaof'.

*** Guile now claims to have the `current-time' feature.

*** The `mktime' function now takes an optional second argument ZONE,
giving the time zone to use for the conversion.  ZONE should be a
string, in the same format as expected for the "TZ" environment variable.

*** The `strptime' function now returns a pair (TIME . COUNT), where
TIME is the parsed time as a vector, and COUNT is the number of
characters from the string left unparsed.  This function used to
return the remaining characters as a string.

*** The `gettimeofday' function has replaced the old `time+ticks' function.
The return value is now (SECONDS . MICROSECONDS); the fractional
component is no longer expressed in "ticks".

*** The `ticks/sec' constant has been removed, in light of the above change.

* Changes to the gh_ interface

** gh_eval_str() now returns an SCM object which is the result of the
evaluation

** gh_scm2str() now copies the Scheme data to a caller-provided C
array

** gh_scm2newstr() now makes a C array, copies the Scheme data to it,
and returns the array

** gh_scm2str0() is gone: there is no need to distinguish
null-terminated from non-null-terminated, since gh_scm2newstr() allows
the user to interpret the data both ways.

* Changes to the scm_ interface

** The new function scm_symbol_value0 provides an easy way to get a
symbol's value from C code:

SCM scm_symbol_value0 (char *NAME)
  Return the value of the symbol named by the null-terminated string
  NAME in the current module.  If the symbol named NAME is unbound in
  the current module, return SCM_UNDEFINED.

** The new function scm_sysintern0 creates new top-level variables,
without assigning them a value.

SCM scm_sysintern0 (char *NAME)
  Create a new Scheme top-level variable named NAME.  NAME is a
  null-terminated string.  Return the variable's value cell.

** The function scm_internal_catch is the guts of catch.  It handles
all the mechanics of setting up a catch target, invoking the catch
body, and perhaps invoking the handler if the body does a throw.

The function is designed to be usable from C code, but is general
enough to implement all the semantics Guile Scheme expects from throw.

TAG is the catch tag.  Typically, this is a symbol, but this function
doesn't actually care about that.

BODY is a pointer to a C function which runs the body of the catch;
this is the code you can throw from.  We call it like this:
   BODY (BODY_DATA, JMPBUF)
where:
   BODY_DATA is just the BODY_DATA argument we received; we pass it
      through to BODY as its first argument.  The caller can make
      BODY_DATA point to anything useful that BODY might need.
   JMPBUF is the Scheme jmpbuf object corresponding to this catch,
      which we have just created and initialized.

HANDLER is a pointer to a C function to deal with a throw to TAG,
should one occur.  We call it like this:
   HANDLER (HANDLER_DATA, THROWN_TAG, THROW_ARGS)
where
   HANDLER_DATA is the HANDLER_DATA argument we recevied; it's the
      same idea as BODY_DATA above.
   THROWN_TAG is the tag that the user threw to; usually this is
      TAG, but it could be something else if TAG was #t (i.e., a
      catch-all), or the user threw to a jmpbuf.
   THROW_ARGS is the list of arguments the user passed to the THROW
      function.

BODY_DATA is just a pointer we pass through to BODY.  HANDLER_DATA
is just a pointer we pass through to HANDLER.  We don't actually
use either of those pointers otherwise ourselves.  The idea is
that, if our caller wants to communicate something to BODY or
HANDLER, it can pass a pointer to it as MUMBLE_DATA, which BODY and
HANDLER can then use.  Think of it as a way to make BODY and
HANDLER closures, not just functions; MUMBLE_DATA points to the
enclosed variables.

Of course, it's up to the caller to make sure that any data a
MUMBLE_DATA needs is protected from GC.  A common way to do this is
to make MUMBLE_DATA a pointer to data stored in an automatic
structure variable; since the collector must scan the stack for
references anyway, this assures that any references in MUMBLE_DATA
will be found.

** The new function scm_internal_lazy_catch is exactly like
scm_internal_catch, except:

- It does not unwind the stack (this is the major difference).
- If handler returns, its value is returned from the throw.
- BODY always receives #f as its JMPBUF argument (since there's no
  jmpbuf associated with a lazy catch, because we don't unwind the
  stack.)

** scm_body_thunk is a new body function you can pass to
scm_internal_catch if you want the body to be like Scheme's `catch'
--- a thunk, or a function of one argument if the tag is #f.

BODY_DATA is a pointer to a scm_body_thunk_data structure, which
contains the Scheme procedure to invoke as the body, and the tag
we're catching.  If the tag is #f, then we pass JMPBUF (created by
scm_internal_catch) to the body procedure; otherwise, the body gets
no arguments.

** scm_handle_by_proc is a new handler function you can pass to
scm_internal_catch if you want the handler to act like Scheme's catch
--- call a procedure with the tag and the throw arguments.

If the user does a throw to this catch, this function runs a handler
procedure written in Scheme.  HANDLER_DATA is a pointer to an SCM
variable holding the Scheme procedure object to invoke.  It ought to
be a pointer to an automatic variable (i.e., one living on the stack),
or the procedure object should be otherwise protected from GC.

** scm_handle_by_message is a new handler function to use with
`scm_internal_catch' if you want Guile to print a message and die.
It's useful for dealing with throws to uncaught keys at the top level.

HANDLER_DATA, if non-zero, is assumed to be a char * pointing to a
message header to print; if zero, we use "guile" instead.  That
text is followed by a colon, then the message described by ARGS.

** The return type of scm_boot_guile is now void; the function does
not return a value, and indeed, never returns at all.

** The new function scm_shell makes it easy for user applications to
process command-line arguments in a way that is compatible with the
stand-alone guile interpreter (which is in turn compatible with SCSH,
the Scheme shell).

To use the scm_shell function, first initialize any guile modules
linked into your application, and then call scm_shell with the values
of ARGC and ARGV your `main' function received.  scm_shell will adding
any SCSH-style meta-arguments from the top of the script file to the
argument vector, and then process the command-line arguments.  This
generally means loading a script file or starting up an interactive
command interpreter.  For details, see "Changes to the stand-alone
interpreter" above.

** The new functions scm_get_meta_args and scm_count_argv help you
implement the SCSH-style meta-argument, `\'.  

char **scm_get_meta_args (int ARGC, char **ARGV)
  If the second element of ARGV is a string consisting of a single
  backslash character (i.e. "\\" in Scheme notation), open the file
  named by the following argument, parse arguments from it, and return
  the spliced command line.  The returned array is terminated by a
  null pointer.
  
  For details of argument parsing, see above, under "guile now accepts
  command-line arguments compatible with SCSH..."

int scm_count_argv (char **ARGV)
  Count the arguments in ARGV, assuming it is terminated by a null
  pointer.

For an example of how these functions might be used, see the source
code for the function scm_shell in libguile/script.c.

You will usually want to use scm_shell instead of calling this
function yourself.

** The new function scm_compile_shell_switches turns an array of
command-line arguments into Scheme code to carry out the actions they
describe.  Given ARGC and ARGV, it returns a Scheme expression to
evaluate, and calls scm_set_program_arguments to make any remaining
command-line arguments available to the Scheme code.  For example,
given the following arguments:

        -e main -s ekko a speckled gecko

scm_set_program_arguments will return the following expression:

        (begin (load "ekko") (main (command-line)) (quit))

You will usually want to use scm_shell instead of calling this
function yourself.

** The function scm_shell_usage prints a usage message appropriate for
an interpreter that uses scm_compile_shell_switches to handle its
command-line arguments.

void scm_shell_usage (int FATAL, char *MESSAGE)
  Print a usage message to the standard error output.  If MESSAGE is
  non-zero, write it before the usage message, followed by a newline.
  If FATAL is non-zero, exit the process, using FATAL as the
  termination status.  (If you want to be compatible with Guile,
  always use 1 as the exit status when terminating due to command-line
  usage problems.)

You will usually want to use scm_shell instead of calling this
function yourself.

** scm_eval_0str now returns SCM_UNSPECIFIED if the string contains no
expressions.  It used to return SCM_EOL.  Earth-shattering.

** The macros for declaring scheme objects in C code have been
rearranged slightly.  They are now:

SCM_SYMBOL (C_NAME, SCHEME_NAME)
  Declare a static SCM variable named C_NAME, and initialize it to
  point to the Scheme symbol whose name is SCHEME_NAME.  C_NAME should
  be a C identifier, and SCHEME_NAME should be a C string.

SCM_GLOBAL_SYMBOL (C_NAME, SCHEME_NAME)
  Just like SCM_SYMBOL, but make C_NAME globally visible.

SCM_VCELL (C_NAME, SCHEME_NAME)
  Create a global variable at the Scheme level named SCHEME_NAME.
  Declare a static SCM variable named C_NAME, and initialize it to
  point to the Scheme variable's value cell.

SCM_GLOBAL_VCELL (C_NAME, SCHEME_NAME)
  Just like SCM_VCELL, but make C_NAME globally visible.

The `guile-snarf' script writes initialization code for these macros
to its standard output, given C source code as input.

The SCM_GLOBAL macro is gone.

** The scm_read_line and scm_read_line_x functions have been replaced
by Scheme code based on the %read-delimited! procedure (known to C
code as scm_read_delimited_x).  See its description above for more
information.

** The function scm_sys_open has been renamed to scm_open.  It now
returns a port instead of an FD object.

* The dynamic linking support has changed.  For more information, see
libguile/DYNAMIC-LINKING.

\f
Guile 1.0b3

User-visible changes from Thursday, September 5, 1996 until Guile 1.0
(Sun 5 Jan 1997):

* Changes to the 'guile' program:

** Guile now loads some new files when it starts up.  Guile first
searches the load path for init.scm, and loads it if found.  Then, if
Guile is not being used to execute a script, and the user's home
directory contains a file named `.guile', Guile loads that.

** 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.

Now you can use Guile as an interpreter, using a mechanism which is a
compatible subset of that provided by SCSH.

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.  Furthermore, if the path to Guile on your system
is too long for your kernel, you can start the script with this
horrible hack:

#!/bin/sh
exec /really/long/path/to/guile -s "$0" ${1+"$@"}
!#

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 read-eval-print loop no longer prints #<unspecified>
results.  If the user wants to see this, she can evaluate the
expression (assert-repl-print-unspecified #t), perhaps in her startup
file.

** Guile no longer shows backtraces by default when an error occurs;
however, it does display a message saying how to get one, and how to
request that they be displayed by default.  After an error, evaluate
   (backtrace)
to see a backtrace, and
   (debug-enable 'backtrace)
to see them by default.



* Changes to Guile Scheme:

** 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.


** Guile's delq, delv, delete functions, and their destructive
counterparts, delq!, delv!, and delete!, now remove all matching
elements from the list, not just the first.  This matches the behavior
of the corresponding Emacs Lisp functions, and (I believe) the Maclisp
functions which inspired them.

I recognize that this change may break code in subtle ways, but it
seems best to make the change before the FSF's first Guile release,
rather than after.


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

** The facilities for loading Scheme source files have changed.

*** 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.

*** The variable %load-extensions now tells Guile which extensions to
try appending to a filename when searching the load path.  Its value
is a list of strings.  Its default value is ("" ".scm").

*** (%search-load-path FILENAME) searches the directories listed in the
value of the %load-path variable for a Scheme file named FILENAME,
with all the extensions listed in %load-extensions.  If it finds a
match, then it returns its full filename.  If FILENAME is absolute, it
returns it unchanged.  Otherwise, it returns #f.

%search-load-path will not return matches that refer to directories.

*** (primitive-load FILENAME :optional CASE-INSENSITIVE-P SHARP)
uses %seach-load-path to find 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
`read' function.

*** load uses the same searching semantics as primitive-load.

*** The functions %try-load, try-load-with-path, %load, load-with-path,
basic-try-load-with-path, basic-load-with-path, try-load-module-with-
path, and load-module-with-path have been deleted.  The functions
above should serve their purposes.

*** If the value of the variable %load-hook is a procedure,
`primitive-load' applies its value to the name of the file being
loaded (without the load path directory name prepended).  If its value
is #f, it is ignored.  Otherwise, an error occurs.

This is mostly useful for printing load notification messages.


** The function `eval!' is no longer accessible from the scheme level.
We can't allow operations which introduce glocs into the scheme level,
because Guile's type system can't handle these as data.  Use `eval' or
`read-and-eval!' (see below) as replacement.

** The new function read-and-eval! reads an expression from PORT,
evaluates it, and returns the result.  This is more efficient than
simply calling `read' and `eval', since it is not necessary to make a
copy of the expression for the evaluator to munge.

Its optional arguments CASE_INSENSITIVE_P and SHARP are interpreted as
for the `read' function.


** The function `int?' has been removed; its definition was identical
to that of `integer?'.

** The functions `<?', `<?', `<=?', `=?', `>?', and `>=?'.  Code should
use the R4RS names for these functions.

** The function object-properties no longer returns the hash handle;
it simply returns the object's property list.

** Many functions have been changed to throw errors, instead of
returning #f on failure.  The point of providing exception handling in
the language is to simplify the logic of user code, but this is less
useful if Guile's primitives don't throw exceptions.

** The function `fileno' has been renamed from `%fileno'.

** The function primitive-mode->fdes returns #t or #f now, not 1 or 0.


* Changes to Guile's C interface:

** The library's initialization procedure has been simplified.
scm_boot_guile now has the prototype:

void scm_boot_guile (int ARGC,
                     char **ARGV,
                     void (*main_func) (),
                     void *closure);

scm_boot_guile calls MAIN_FUNC, passing it CLOSURE, ARGC, and ARGV.
MAIN_FUNC should do all the work of the program (initializing other
packages, reading user input, etc.) before returning.  When MAIN_FUNC
returns, call exit (0); this function never returns.  If you want some
other exit value, MAIN_FUNC may call exit itself.

scm_boot_guile arranges for program-arguments to return the strings
given by ARGC and ARGV.  If MAIN_FUNC modifies ARGC/ARGV, should call
scm_set_program_arguments with the final list, so Scheme code will
know which arguments have been processed.

scm_boot_guile establishes a catch-all catch handler which prints an
error message and exits the process.  This means that Guile exits in a
coherent way when system errors occur and the user isn't prepared to
handle it.  If the user doesn't like this behavior, they can establish
their own universal catcher in MAIN_FUNC to shadow this one.

Why must the caller do all the real work from MAIN_FUNC?  The garbage
collector assumes that all local variables of type SCM will be above
scm_boot_guile's stack frame on the stack.  If you try to manipulate
SCM values after this function returns, it's the luck of the draw
whether the GC will be able to find the objects you allocate.  So,
scm_boot_guile function exits, rather than returning, to discourage
people from making that mistake.

The IN, OUT, and ERR arguments were removed; there are other
convenient ways to override these when desired.

The RESULT argument was deleted; this function should never return.

The BOOT_CMD argument was deleted; the MAIN_FUNC argument is more
general.


** 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.


** Two new C functions, scm_protect_object and scm_unprotect_object,
have been added to the Guile library.

scm_protect_object (OBJ) protects OBJ from the garbage collector.
OBJ will not be freed, even if all other references are dropped,
until someone does scm_unprotect_object (OBJ).  Both functions
return OBJ.

Note that calls to scm_protect_object do not nest.  You can call
scm_protect_object any number of times on a given object, and the
next call to scm_unprotect_object will unprotect it completely.

Basically, scm_protect_object and scm_unprotect_object just
maintain a list of references to things.  Since the GC knows about
this list, all objects it mentions stay alive.  scm_protect_object
adds its argument to the list; scm_unprotect_object remove its
argument from the list.


** scm_eval_0str now returns the value of the last expression
evaluated.

** The new function scm_read_0str reads an s-expression from a
null-terminated string, and returns it.

** The new function `scm_stdio_to_port' converts a STDIO file pointer
to a Scheme port object.

** The new function `scm_set_program_arguments' allows C code to set
the value teruturned by the Scheme `program-arguments' function.

\f
Older changes:

* Guile no longer includes sophisticated Tcl/Tk support.

The old Tcl/Tk support was unsatisfying to us, because it required the
user to link against the Tcl library, as well as Tk and Guile.  The
interface was also un-lispy, in that it preserved Tcl/Tk's practice of
referring to widgets by names, rather than exporting widgets to Scheme
code as a special datatype.

In the Usenix Tk Developer's Workshop held in July 1996, the Tcl/Tk
maintainers described some very interesting changes in progress to the
Tcl/Tk internals, which would facilitate clean interfaces between lone
Tk and other interpreters --- even for garbage-collected languages
like Scheme.  They expected the new Tk to be publicly available in the
fall of 1996.

Since it seems that Guile might soon have a new, cleaner interface to
lone Tk, and that the old Guile/Tk glue code would probably need to be
completely rewritten, we (Jim Blandy and Richard Stallman) have
decided not to support the old code.  We'll spend the time instead on
a good interface to the newer Tk, as soon as it is available.

Until then, gtcltk-lib provides trivial, low-maintenance functionality.

\f
Copyright information:

Copyright (C) 1996,1997 Free Software Foundation, Inc.

   Permission is granted to anyone to make or distribute verbatim copies
   of this document as received, in any medium, provided that the
   copyright notice and this permission notice are preserved,
   thus giving the recipient permission to redistribute in turn.

   Permission is granted to distribute modified versions
   of this document, or of portions of it,
   under the above conditions, provided also that they
   carry prominent notices stating who last changed them.

\f
Local variables:
mode: outline
paragraph-separate: "[  \f]*$"
end: