Update copyright.

Add index in header comments.

(AC_GUILE_MODULE_CHECK, AC_GUILE_MODULE_AVAILABLE,
AC_GUILE_MODULE_REQUIRED): New macros.

guile-config/guile.m4

@@ -1,34 +1,34 @@
-dnl   Automake macros for working with Guile.
+dnl   Autoconf macros for working with Guile.
-dnl   
+dnl
-dnl   	Copyright (C) 1998 Free Software Foundation, Inc.
+dnl   	Copyright (C) 1998,2001 Free Software Foundation, Inc.
-dnl   
+dnl
 dnl   This program is free software; you can redistribute it and/or modify
 dnl   it under the terms of the GNU General Public License as published by
 dnl   the Free Software Foundation; either version 2, or (at your option)
 dnl   any later version.
-dnl   
+dnl
 dnl   This program is distributed in the hope that it will be useful,
 dnl   but WITHOUT ANY WARRANTY; without even the implied warranty of
 dnl   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 dnl   GNU General Public License for more details.
-dnl   
+dnl
 dnl   You should have received a copy of the GNU General Public License
 dnl   along with this software; see the file COPYING.  If not, write to
 dnl   the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 dnl   Boston, MA 02111-1307 USA
-dnl   
+dnl
 dnl   As a special exception, the Free Software Foundation gives permission
 dnl   for additional uses of the text contained in its release of GUILE.
-dnl   
+dnl
 dnl   The exception is that, if you link the GUILE library with other files
 dnl   to produce an executable, this does not by itself cause the
 dnl   resulting executable to be covered by the GNU General Public License.
 dnl   Your use of that executable is in no way restricted on account of
 dnl   linking the GUILE library code into it.
-dnl   
+dnl
 dnl   This exception does not however invalidate any other reasons why
 dnl   the executable file might be covered by the GNU General Public License.
-dnl   
+dnl
 dnl   This exception applies only to the code released by the
 dnl   Free Software Foundation under the name GUILE.  If you copy
 dnl   code from other Free Software Foundation releases into a copy of
@@ -36,14 +36,26 @@ dnl   GUILE, as the General Public License permits, the exception does
 dnl   not apply to the code that you add in this way.  To avoid misleading
 dnl   anyone as to the status of such modified files, you must delete
 dnl   this exception notice from them.
-dnl   
+dnl
 dnl   If you write modifications of your own for GUILE, it is your choice
 dnl   whether to permit this exception to apply to your modifications.
 dnl   If you do not wish that, delete this exception notice.
 
 
+dnl   INDEX
+dnl   -----
+
 dnl   GUILE_FLAGS --- set flags for compiling and linking with Guile
-dnl 
+dnl   AC_GUILE_MODULE_CHECK --- check feature of a Guile Scheme module
+dnl   AC_GUILE_MODULE_AVAILABLE --- check availability of a Guile Scheme module
+dnl   AC_GUILE_MODULE_REQUIRED --- fail if a Guile Scheme module is unavailable
+
+
+dnl   Code
+dnl   ----
+
+dnl   GUILE_FLAGS --- set flags for compiling and linking with Guile
+dnl
 dnl   This macro runs the `guile-config' script, installed with Guile,
 dnl   to find out where Guile's header files and libraries are
 dnl   installed.  It sets two variables, marked for substitution, as
@@ -74,3 +86,47 @@ AC_DEFUN([GUILE_FLAGS],[
   AC_SUBST(GUILE_LDFLAGS)
   AC_MSG_RESULT(yes)
 ])
+
+
+dnl   AC_GUILE_MODULE_CHECK --- check feature of a Guile Scheme module
+dnl
+dnl   AC_GUILE_MODULE_CHECK(var,module,featuretest,description)
+dnl   $1 is a shell variable name to be set to "yes" or "no"
+dnl   $2 is a list of symbols, like: (ice-9 common-list)
+dnl   $3 is a thunk, like: (lambda () BODY ...)
+dnl      which returns either 0 or #t to indicate the check passed.
+dnl      avoid using the character "#" since that confuses autoconf.
+dnl   $4 is a noun phrase passed to AC_MSG_CHECKING
+
+AC_DEFUN([AC_GUILE_MODULE_CHECK],
+         [AC_MSG_CHECKING([$2 $4])
+          $1=no
+          echo '(use-modules $2) (exit ($3))' > conftest
+          guile -s conftest > /dev/null 2>&1 && $1=yes
+          rm -f conftest
+          AC_MSG_RESULT($[$1])
+         ])
+
+dnl   AC_GUILE_MODULE_AVAILABLE --- check availability of a Guile Scheme module
+dnl
+dnl   AC_GUILE_MODULE_AVAILABLE(var,module)
+dnl   $1 is a shell variable name to be set to "yes" or "no"
+dnl   $2 is a list of symbols, like: (ice-9 common-list)
+
+AC_DEFUN([AC_GUILE_MODULE_AVAILABLE],
+         [AC_GUILE_MODULE_CHECK($1,$2,(lambda () 0),availability)
+         ])
+
+dnl   AC_GUILE_MODULE_REQUIRED --- fail if a Guile Scheme module is unavailable
+dnl
+dnl   $1 is a list of symbols, WITHOUT the surrounding parens
+
+AC_DEFUN([AC_GUILE_MODULE_REQUIRED],
+         [AC_GUILE_MODULE_AVAILABLE(ac_guile_module_required, ($1))
+          if test "$ac_guile_module_required" = "no" ; then
+              AC_MSG_ERROR([required guile module not found: ($1)])
+          fi
+         ])
+
+
+dnl   guile.m4 ends here