bug476.m:058: In instance declaration for `input_stream'/1:
bug476.m:058:   the type class has no predicate method named `mark'/4.
bug476.m:068: Error: pred `bug476.mark'/4 multiply defined.
bug476.m:034: Here is the previous definition of pred `bug476.mark'/4.
bug476.m:070: Error: clause for predicate `input_stream_mark'/3
bug476.m:070:   without corresponding `:- pred' declaration.