Hi :) On Tue 20 Apr 2010 01:12, l...@gnu.org (Ludovic Courtès) writes:
> Andy Wingo <wi...@pobox.com> writes: > >> I recently added a global fluid, %file-port-name-canonicalization, which >> defaults to #f. But if it's 'absolute, the port name of a file port will >> be canonicalized to the absolute path; or, if it's 'relative, the port >> name is the canonical name of the file, relative to the %load-path, or >> the file name as given otherwise. >> >> The intention was to allow the user to control (port-filename P), so >> that the user could find e.g. the absolute path corresponding to that >> port at the time that it was made. > > My feeling is that ports shouldn’t have to deal with paths because > that’s a separate concern. The %file-port-name-canonicalization fluid > seems like an inelegant hack to me. > > When applications have special requirements about paths, then it should > be up to the application logic to deal with that. I am inclined to agree. A few complications cloud my view, though. 1. While ports do not have anything to do with file names / paths, *file* ports certainly do -- because not only do they use the given path to open the file, they set that path as the port's filename, providing the only means for reverse-mapping ports to filenames (which is the end goal here, reverse-mapping objects to filenames). 2. I think a fluid is still necessary, because a file being compiled can do an `include' or `include-from-path', or even `open-input-file' in a macro, and all these cases you would want the same %file-port-name-canonicalization to take effect. 3. The only correct time to do a path canonicalization is when the file is opened, because at another time, you might not be in the same current directory, so relative paths would resolve incorrectly. 4. The application-level code is nastier if it has to canonicalize, because a relative canonicalization cannot in general be passed to open-input-file. For example (open-input-file "../../module/ice-9/boot-9.scm") is not the same as (open-input-file "ice-9/boot-9.scm") So you'd have to do a set-port-filename! on the port, mucking up your code -- and how would you decide what to set? In N places you'd have to duplicate fport_canonicalize_filename, and you'd probably have to make scm_i_relativize_path public. When I realized all of that I decided to go with the minimal correct solution, though it is a bit hacky. Applications are still free to do their own thing, as %file-port-name-canonicalization defaults to #f, but the useful 'absolute and 'relative behaviors are more convenient and robust. I'd be happy to have some cleaner solution, though. Do you have any ideas? Cheers, Andy -- http://wingolog.org/
