> I hope that's of some use. thanks. in racket 5.1 scheme_display_to_string defined as this in schemef.h: scheme_display_to_string(Scheme_Object*, intptr_t*) it seems that in your version it was defined as this: scheme_display_to_string(Scheme_Object*, long int*) do you have the latest racket 5.1 release? best, gabor