+
+Return the result of calling FUNCTION with the first and the
+second element of SEQ, then calling FUNCTION with that result and
+the third element of SEQ, then with that result and the fourth
+element of SEQ, etc.
+
+If :INITIAL-VALUE is specified, it is added to the front of SEQ.
+If SEQ is empty, return :INITIAL-VALUE and FUNCTION is not
+called.
+