dnl
dnl Check Bison version
dnl AC_PROG_BISON([MIN_VERSION=2.4])
dnl
dnl Will define BISON_USE_PARSER_H_EXTENSION if Automake is < 1.11
dnl for use with .h includes.
dnl

AC_DEFUN([AC_PROG_BISON], [
if test "x$1" = "x" ; then
  bison_required_version="2.4"
else
  bison_required_version="$1"
fi

AC_CHECK_PROG(have_prog_bison, [bison], [yes],[no])

AC_DEFINE_UNQUOTED([BISON_VERSION], [0.0], [Bison version if bison is not available])

#Do not use *.h extension for parser header files, use newer *.hh
bison_use_parser_h_extension=false

if test "$have_prog_bison" = "yes" ; then
  AC_MSG_CHECKING([for bison version >= $bison_required_version])
  bison_version=`bison --version | head -n 1 | cut '-d ' -f 4`
  AC_DEFINE_UNQUOTED([BISON_VERSION], [$bison_version], [Defines bison version])
  if test "$bison_version" \< "$bison_required_version" ; then
    BISON=:
    AC_MSG_RESULT([no])
    AC_MSG_ERROR([Bison version $bison_required_version or higher must be installed on the system!])
  else
    AC_MSG_RESULT([yes])
    BISON=bison
    AC_SUBST(BISON)

    #Verify automake version 1.11 headers for yy files are .h, > 1.12 uses .hh
    automake_version=`automake --version | head -n 1 | cut '-d ' -f 4`
    AC_DEFINE_UNQUOTED([AUTOMAKE_VERSION], [$automake_version], [Defines automake version])

    if test "$automake_version" \< "1.12" ; then
      #Use *.h extension for parser header file
      bison_use_parser_h_extension=true
      echo "Automake version < 1.12"
      AC_DEFINE([BISON_USE_PARSER_H_EXTENSION], [1], [Use *.h extension for parser header file])
    fi
  fi
else
  BISON=:
  AC_MSG_RESULT([NO])
fi

AM_CONDITIONAL([BISON_USE_PARSER_H_EXTENSION], [test x$bison_use_parser_h_extension = xtrue])
AC_SUBST(BISON)
])