l...@gnu.org (Ludovic Courtès) writes: > Hi, > > Andreas Rottmann <a.rottm...@gmx.at> writes: > >> - Ikarus and Ypsilon definitly have disjoint ports. >> >> - Racket natively has ports that will accept both binary and textual >> operations, but it's R6RS support wraps these ports so that the >> resulting R6RS ports are not compatible with Racket's native port >> operations, but do provide the binary/textual disjointness. > > So Racket really has 3 disjoint port types, right? That looks > inconvenient to me. > It is, at least if you don't deal with R6RS-mode code only. It's a similiar situation (although not as pervasively inconvinient) as the mutable/immutable pair division.
>> These are the only implementations (besides Guile), that I'm familiar >> with. Ideally, Guile's R6RS support would provide real disjointness for >> binary and textual ports -- I think the only artefact that hampers this >> is that there's no way to distinguish Latin-1 encoded ports from "pure" >> binary ports (as both have `port-encoding' being #f). > > And beyond that, you can put-bytevector on any port, read-char on any > port, and so on. > > I wouldn’t want the “native” port type to be disjoint from the R6RS port > types, notably because there’s no “native” equivalent to the R6RS binary > I/O API, and also because it would hamper composition of R6RS and > non-R6RS code. > Well, I'm not advocating making them disjoint in the sense that the textual or binary operations are only possible on "matching" ports. Allowing to mix binary and textual I/O on any port, is, IMHO, a fine and reasonable implementation-specific extension that Guile provides. What I'm after is making `textual-port?' and `binary-port?' establish a partition on the set of possible ports; i.e. (textual-port? X) = (not (binary-port? X)) for any port X (or at least for any port obtainable via R6RS-specified procedures). For that to work, we somehow need to distinguish between Latin-1 ports and "pure" binary ports. Perhaps by adding a flag indicating this to the port objects? This flag would then be set by all R6RS procedures specified to create binary ports, and would be checked by `binary-port?' and `textual-port?'. Additionally, we might want to clear that flag when the port's encoding is changed to non-#f. WDYT? Regards, Rotty -- Andreas Rottmann -- <http://rotty.yi.org/>