dnl AS_AC_EXPAND(VAR, CONFIGURE_VAR)

dnl

dnl example

dnl AS_AC_EXPAND(SYSCONFDIR, $sysconfdir)

dnl will set SYSCONFDIR to /usr/local/etc if prefix=/usr/local

AC_DEFUN([AS_AC_EXPAND],

[

  EXP_VAR=[$1]

  FROM_VAR=[$2]

  dnl first expand prefix and exec_prefix if necessary

  prefix_save=$prefix

  exec_prefix_save=$exec_prefix

  dnl if no prefix given, then use /usr/local, the default prefix

  if test "x$prefix" = "xNONE"; then

    prefix=$ac_default_prefix

  fi

  dnl if no exec_prefix given, then use prefix

  if test "x$exec_prefix" = "xNONE"; then

    exec_prefix=$prefix

  fi

  full_var="$FROM_VAR"

  dnl loop until it doesn't change anymore

  while true; do

    new_full_var="`eval echo $full_var`"

    if test "x$new_full_var"="x$full_var"; then break; fi

    full_var=$new_full_var

  done

  dnl clean up

  full_var=$new_full_var

  AC_SUBST([$1], "$full_var")

  dnl restore prefix and exec_prefix

  prefix=$prefix_save

  exec_prefix=$exec_prefix_save

])