Derick Eddington wrote: > Closing string input ports or string output ports changes them from > textual to binary and they are no longer considered input or output > ports. Ikarus, PLT, and Ypsilon don't do this. I'm not sure what R6RS > requires about this,
The R6RS library 8.2.6 specification of close-port says a closed port is still a port, but does not say a closed input port is still an input port, nor does it say a closed output port is still an output port. In fact, it says the opposite, albeit not as explicitly as it should have. The R6RS library 8.2.6 specification of transcoded-port says the closed binary port "cannot be used by the input and output operations described in this chapter." The specifications of those operations, e.g. port-eof? and flush-output-port, say they accept an input-port or an output-port as their argument. If a closed port were still an input-port or an output-port, then a closed port would be acceptable as an input to one of those procedures. Since the R6RS library document says a closed port is not acceptable to the port-eof? and flush-output-port procedures, a closed port cannot be an input port or an output port. That means the behavior of Ikarus, PLT, and Ypsilon is not consistent with R6RS library chapter 8. > but this is unexpected and could cause serious confusion. The R6RS mandates many behaviors that are unexpected and could cause serious confusion. In this case, however, Larceny's R6RS-conforming behavior is consistent with long-standing practice in R5 Scheme, and is less confusing than having input ports for which port-eof? would raise an exception or having output ports for which flush-output-port would raise an exception. The confusion, it would seem, comes from the violation of R6RS semantics by Ikarus, PLT, and Ypsilon. The fact that Larceny's binary-port? predicate returns true for a closed port is a bug, which we will fix. As explained above, the R6RS library document requires binary-port? to return false when its argument is a closed port. Will _______________________________________________ Larceny-users mailing list Larceny-users@lists.ccs.neu.edu https://lists.ccs.neu.edu/bin/listinfo/larceny-users
