AC_DEFUN([AG_GST_BISON_CHECK],

[

  dnl FIXME: check if AC_PROG_YACC is suitable here

  dnl FIXME: make precious

  AC_PATH_PROG(BISON_PATH, bison, no)

  if test x$BISON_PATH = xno; then

    AC_MSG_ERROR(Could not find bison)

  fi

  dnl check bison version

  dnl we need version >= 2.4 for the '<>' support

  dnl in the parser.

  dnl First lines observed: 'bison (GNU Bison) 2.3' or 'GNU Bison version 1.28'

  bison_min_version=2.4

  bison_version=`$BISON_PATH --version | head -n 1 |  sed 's/^[[^0-9]]*//' | sed 's/[[^0-9]]*$//' | cut -d' ' -f1`

  AC_MSG_CHECKING([bison version $bison_version >= $bison_min_version])

  if perl -we "exit (('v$bison_version' ge 'v$bison_min_version') ? 0 : 1)"; then

    AC_MSG_RESULT([yes])

  else

    AC_MSG_ERROR([no])

  fi

])

AC_DEFUN([AG_GST_FLEX_CHECK],

[

  dnl we require flex for building the parser

  AC_PATH_PROG(FLEX_PATH, flex, no)

  if test x$FLEX_PATH = xno; then

    AC_MSG_ERROR(Could not find flex)

  fi

  dnl check flex version

  dnl we need version >= 2.5.31 for the reentrancy support

  dnl in the parser.

  flex_min_version=2.5.31

  flex_version=`$FLEX_PATH --version | head -n 1 | awk '{print $2}'`

  AC_MSG_CHECKING([flex version $flex_version >= $flex_min_version])

  if perl -w <

    (\$min_version_major, \$min_version_minor, \$min_version_micro ) = "$flex_min_version" =~ /(\d+)\.(\d+)\.(\d+)/;

    (\$flex_version_major, \$flex_version_minor, \$flex_version_micro ) = "$flex_version" =~ /(\d+)\.(\d+)\.(\d+)/;

    exit (((\$flex_version_major > \$min_version_major) ||

     ((\$flex_version_major == \$min_version_major) &&

      (\$flex_version_minor > \$min_version_minor)) ||

     ((\$flex_version_major == \$min_version_major) &&

      (\$flex_version_minor == \$min_version_minor) &&

      (\$flex_version_micro >= \$min_version_micro)))

     ? 0 : 1);

EOF

  then

    AC_MSG_RESULT(yes)

  else

    AC_MSG_ERROR([no])

  fi

])