##### http://autoconf-archive.cryp.to/acx_lapack.html
#
# SYNOPSIS
#
#   ACX_LAPACK([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])
#
# DESCRIPTION
#
#   This macro looks for a library that implements the LAPACK
#   linear-algebra interface (see http://www.netlib.org/lapack/). On
#   success, it sets the LAPACK_LIBS output variable to hold the
#   requisite library linkages.
#
#   To link with LAPACK, you should link with:
#
#       $LAPACK_LIBS $BLAS_LIBS $LIBS $FLIBS
#
#   in that order. BLAS_LIBS is the output variable of the ACX_BLAS
#   macro, called automatically. FLIBS is the output variable of the
#   AC_F77_LIBRARY_LDFLAGS macro (called if necessary by ACX_BLAS), and
#   is sometimes necessary in order to link with F77 libraries. Users
#   will also need to use AC_F77_DUMMY_MAIN (see the autoconf manual),
#   for the same reason.
#
#   The user may also use --with-lapack=<lib> in order to use some
#   specific LAPACK library <lib>. In order to link successfully,
#   however, be aware that you will probably need to use the same
#   Fortran compiler (which can be set via the F77 env. var.) as was
#   used to compile the LAPACK and BLAS libraries.
#
#   ACTION-IF-FOUND is a list of shell commands to run if a LAPACK
#   library is found, and ACTION-IF-NOT-FOUND is a list of commands to
#   run it if it is not found. If ACTION-IF-FOUND is not specified, the
#   default action will define HAVE_LAPACK.
#
# LAST MODIFICATION
#
#   2002-03-12
#
# COPYLEFT
#
#   Copyright (c) 2002 Steven G. Johnson <stevenj@alum.mit.edu>
#
#   This program is free software; you can redistribute it and/or
#   modify it under the terms of the GNU General Public License as
#   published by the Free Software Foundation; either version 2 of the
#   License, or (at your option) any later version.
#
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#   WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#   General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
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#   make and distribute a modified version of the Autoconf Macro, you
#   may extend this special exception to the GPL to apply to your
#   modified version as well.

AC_DEFUN([ACX_LAPACK], [
AC_REQUIRE([ACX_BLAS])
acx_lapack_ok=no

AC_ARG_WITH(lapack,
        [AC_HELP_STRING([--with-lapack=<lib>], [use LAPACK library <lib>])])
case $with_lapack in
        yes | "") ;;
        no) acx_lapack_ok=disable ;;
        -* | */* | *.a | *.so | *.so.* | *.o) LAPACK_LIBS="$with_lapack" ;;
        *) LAPACK_LIBS="-l$with_lapack" ;;
esac

# Get fortran linker name of LAPACK function to check for.
AC_F77_FUNC(cheev)

# We cannot use LAPACK if BLAS is not found
if test "x$acx_blas_ok" != xyes; then
        acx_lapack_ok=noblas
fi

# First, check LAPACK_LIBS environment variable
if test "x$LAPACK_LIBS" != x; then
        save_LIBS="$LIBS"; LIBS="$LAPACK_LIBS $BLAS_LIBS $LIBS $FLIBS"
        AC_MSG_CHECKING([for $cheev in $LAPACK_LIBS])
        AC_TRY_LINK_FUNC($cheev, [acx_lapack_ok=yes], [LAPACK_LIBS=""])
        AC_MSG_RESULT($acx_lapack_ok)
        LIBS="$save_LIBS"
        if test acx_lapack_ok = no; then
                LAPACK_LIBS=""
        fi
fi

# LAPACK linked to by default?  (is sometimes included in BLAS lib)
if test $acx_lapack_ok = no; then
        save_LIBS="$LIBS"; LIBS="$LIBS $BLAS_LIBS $FLIBS"
        AC_CHECK_FUNC($cheev, [acx_lapack_ok=yes])
        LIBS="$save_LIBS"
fi

# Generic LAPACK library?
for lapack in lapack lapack_rs6k; do
        if test $acx_lapack_ok = no; then
                save_LIBS="$LIBS"; LIBS="$BLAS_LIBS $LIBS"
                AC_CHECK_LIB($lapack, $cheev,
                    [acx_lapack_ok=yes; LAPACK_LIBS="-l$lapack"], [], [$FLIBS])
                LIBS="$save_LIBS"
        fi
done

AC_SUBST(LAPACK_LIBS)

# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
if test x"$acx_lapack_ok" = xyes; then
        ifelse([$1],,AC_DEFINE(HAVE_LAPACK,1,[Define if you have LAPACK library.]),[$1])
        :
else
        acx_lapack_ok=no
        $2
fi
])dnl ACX_LAPACK