strings containing non-ascii characters are written using either

hex escaping or as-is depending on the value of the print-unicode
parameter.

scheme/ikarus.writer.ss

@@ -405,9 +405,10 @@
                 (write-char c p)]
                [($fx< b 127)
                 (write-char c p)]
-               [(unicode-printable-char? c) 
+               [(print-unicode) 
                 (write-char c p)]
-               [else (write-inline-hex b p)]))
+               [else
+                (write-inline-hex b p)]))
            (loop x (fxadd1 i) n p)))) 
       (write-char #\" p)
       (loop x 0 (string-length x) p)

scheme/last-revision

@@ -1 +1 @@
-1580
+1581