At Mon, 26 Jul 2010 14:29:57 +0200, Laurent wrote: > The reader cannot read #<path:....> forms (is this the right term?). > When the interaction window is in constructor mode, for (build-path "a" > "b"), it writes #<path:a/b>, but this cannot be read back. > > First question: would it be possible to make the reader read paths?
The reason that paths are not `read'able is that's there is not a single right choice for how to marshal paths: * Sometimes you want the string form of a path, which may be encoded in different ways on different platforms (e.g., using different locales) to keep the string form the same. * Sometimes you want the bytes form of a path, because the path isn't going to be used on multiple systems, and converting to a string form may lose information (e.g., because it's not a UTF-8 encoding). Since there was no right answer, we decided not to pick either of them. The lack of a `read'able form is a weak hint to programmers that they need to look closely at the question. > Second question: I need this for my own purposes, so I wrote a > path-constructor: > (define/provide (write-path p) > (cons 'build-path > (map (λ(p-elt)(if (symbol? p-elt) > (list 'quote p-elt) > (path->string p-elt))) > (explode-path p)))) > > > (write-path (build-path 'same 'up "a" "b")) > '(build-path 'same 'up "a" "b") > > Does someone know if this is good enough, or am I omitting something > (platform specific maybe)? As a minimum, use `path-element->string' instead of `path->string'. Otherwise, beware that (as noted above) not all paths have string encodings; depending on your application, that may not be an issue. Or it may be that you want to marshal via byte strings using `bytes->path' as a constructor. _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
