AC_DEFUN([AC_PROG_SWIG],[
        AC_PATH_PROG([SWIG],[swig])
        if test -z "$SWIG" ; then
                AC_MSG_WARN([cannot find 'swig' program. You should look at http://www.swig.org])
                SWIG='echo "Error: SWIG is not installed. You should look at http://www.swig.org" ; false'
        elif test -n "$1" ; then
                AC_MSG_CHECKING([for SWIG version])
                [swig_version=`$SWIG -version 2>&1 | grep 'SWIG Version' | sed 's/.*\([0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\).*/\1/g'`]
                AC_MSG_RESULT([$swig_version])
                if test -n "$swig_version" ; then
                        # Calculate the required version number components
                        [required=$1]
                        [required_major=`echo $required | sed 's/[^0-9].*//'`]
                        if test -z "$required_major" ; then
                                [required_major=0]
                        fi
                        [required=`echo $required | sed 's/[0-9]*[^0-9]//'`]
                        [required_minor=`echo $required | sed 's/[^0-9].*//'`]
                        if test -z "$required_minor" ; then
                                [required_minor=0]
                        fi
                        [required=`echo $required | sed 's/[0-9]*[^0-9]//'`]
                        [required_patch=`echo $required | sed 's/[^0-9].*//'`]
                        if test -z "$required_patch" ; then
                                [required_patch=0]
                        fi
                        # Calculate the available version number components
                        [available=$swig_version]
                        [available_major=`echo $available | sed 's/[^0-9].*//'`]
                        if test -z "$available_major" ; then
                                [available_major=0]
                        fi
                        [available=`echo $available | sed 's/[0-9]*[^0-9]//'`]
                        [available_minor=`echo $available | sed 's/[^0-9].*//'`]
                        if test -z "$available_minor" ; then
                                [available_minor=0]
                        fi
                        [available=`echo $available | sed 's/[0-9]*[^0-9]//'`]
                        [available_patch=`echo $available | sed 's/[^0-9].*//'`]
                        if test -z "$available_patch" ; then
                                [available_patch=0]
                        fi
                        if test $available_major -ne $required_major \
                                -o $available_minor -ne $required_minor \
                                -o $available_patch -lt $required_patch ; then
                                AC_MSG_WARN([SWIG version >= $1 is required.  You have $swig_version.  You should look at http://www.swig.org])
                                SWIG='echo "Error: SWIG version >= $1 is required.  You have '"$swig_version"'.  You should look at http://www.swig.org" ; false'
                        else
                                AC_MSG_NOTICE([SWIG executable is '$SWIG'])
                                SWIG_LIB=`$SWIG -swiglib`
                                AC_MSG_NOTICE([SWIG library directory is '$SWIG_LIB'])
                        fi
                else
                        AC_MSG_WARN([cannot determine SWIG version])
                        SWIG='echo "Error: Cannot determine SWIG version.  You should look at http://www.swig.org" ; false'
                fi
        fi
        AC_SUBST([SWIG_LIB])
])

dnl a macro to check for ability to create python extensions
dnl  AM_CHECK_PYTHON_HEADERS([ACTION-IF-POSSIBLE], [ACTION-IF-NOT-POSSIBLE])
dnl function also defines PYTHON_INCLUDES
AC_DEFUN([AM_CHECK_PYTHON_HEADERS],
[AC_REQUIRE([AM_PATH_PYTHON])
AC_MSG_CHECKING(for headers required to compile python extensions)
dnl deduce PYTHON_INCLUDES
py_prefix=`$PYTHON -c "import sys; print sys.prefix"`
py_exec_prefix=`$PYTHON -c "import sys; print sys.exec_prefix"`
PYTHON_INCLUDES="-I${py_prefix}/include/python${PYTHON_VERSION}"
if test "$py_prefix" != "$py_exec_prefix"; then
  PYTHON_INCLUDES="$PYTHON_INCLUDES -I${py_exec_prefix}/include/python${PYTHON_VERSION}"
fi
AC_SUBST(PYTHON_INCLUDES)
dnl check if the headers exist:
save_CPPFLAGS="$CPPFLAGS"
CPPFLAGS="$CPPFLAGS $PYTHON_INCLUDES"
AC_TRY_CPP([#include <Python.h>],dnl
[AC_MSG_RESULT(found)
$1],dnl
[AC_MSG_RESULT(not found)
$2])
CPPFLAGS="$save_CPPFLAGS"
])