assume given SCALA_HOME, e.g. from component settings or external setup;

--- a/etc/settings	Fri May 28 18:15:53 2010 +0200
+++ b/etc/settings	Fri May 28 20:41:23 2010 +0200
@@ -56,14 +56,6 @@
 ###
 
 ISABELLE_JAVA="java"
-ISABELLE_SCALA="scala"
-
-[ -z "$SCALA_HOME" ] && SCALA_HOME=$(choosefrom \
-  "$ISABELLE_HOME/contrib/scala" \
-  "$ISABELLE_HOME/../scala" \
-  "")
-
-[ -n "$SCALA_HOME" ] && ISABELLE_SCALA="$SCALA_HOME/bin/scala"
 
 classpath "$ISABELLE_HOME/lib/classes/Pure.jar"
 

--- a/lib/Tools/scala	Fri May 28 18:15:53 2010 +0200
+++ b/lib/Tools/scala	Fri May 28 20:41:23 2010 +0200
@@ -4,7 +4,9 @@
 #
 # DESCRIPTION: invoke Scala within the Isabelle environment
 
+[ -z "$SCALA_HOME" ] && { echo "Unknown SCALA_HOME -- Scala unavailable"; exit 2; }
+
 [ -e "$ISABELLE_HOME/Admin/build" ] && { "$ISABELLE_HOME/Admin/build" jars || exit $?; }
 
 CLASSPATH="$(jvmpath "$CLASSPATH")"
-exec "$ISABELLE_SCALA" "$@"
+exec "$SCALA_HOME/bin/scala" "$@"

--- a/src/Pure/build-jars	Fri May 28 18:15:53 2010 +0200
+++ b/src/Pure/build-jars	Fri May 28 20:41:23 2010 +0200
@@ -16,7 +16,7 @@
 }
 
 [ -n "$ISABELLE_HOME" ] || fail "Missing Isabelle settings environment"
-[ -z "$SCALA_HOME" ] && fail "Scala unavailable: unknown SCALA_HOME"
+[ -z "$SCALA_HOME" ] && fail "Unknown SCALA_HOME -- Scala unavailable"
 
 
 ## dependencies