$NetBSD$

Yanked from 'bootstrap' script, so we can apply it earlier.

--- ylwrap.orig	2013-08-30 10:25:30.000000000 +0000
+++ ylwrap
@@ -199,8 +199,24 @@ if test $ret -eq 0; then
       # include guards too.
       FROM=`guard "$from"`
       TARGET=`guard "$to"`
+
+      prefix=`echo $input | sed \
+		-e 's,^.*/,,g' \
+		-e 's/_parse.[yl]$/_/g' \
+		-e 's/_tok.[yl]$/_/g'`
+
+      case $prefix in
+      *.y)
+	      code_prefix="$(basename $prefix _gram.y)_yy";;
+      *.l)
+	      code_prefix="$(basename $prefix _lex.l)_yy";;
+      *)
+	      code_prefix="$prefix";;
+      esac
+
       sed -e "/^#/!b" -e "s|$input_rx|$input_sub_rx|" -e "$rename_sed" \
-          -e "s|$FROM|$TARGET|" "$from" >"$target" || ret=$?
+          -e "s|$FROM|$TARGET|" "$from" | sed -e "s|yy|$code_prefix|g" > \
+	  "$target" || ret=$?
 
       # Check whether files must be updated.
       if test "$from" != "$parser"; then
