On Mon, Jan 02, 2012 at 07:56:13AM -0800, Per Bothner wrote: > On 01/02/2012 01:52 AM, Jeronimo Pellegrini wrote: > >Reading the latest draft I realized that there is no > >standard way to obtain a list of all features (those > >used by cond-expand) declared/supported by an > >implementation. Chibi, Guile and Tinyscheme do keep > >a list in the *features* variable, but it doesn't seem > >to be standard. It would make sense in some situations > >to check/log/report features, maybe not knowing a > >complete list of possible features beforehand. > > As long as the feature list is allowed to be a subset > of all features, mainly to be used for logging. > > Kawa allows class-exists:ClassName as a feature, which > is true if the class ClassName is available (in the classpath) > at macro-expansion time. Obviously a complete list of > features of this form would be expensive to compute.
I see; but I had not thought of this as obligaroty. Something like, "if there is a feature list, then it should be available as a list in the variable *features*", or something similar would perhaps be interesting (although this is not such an immportant thing IMHO). And of course, I was thinking about short feature lists (in the spirit of Appendix B -- "is it POSIX? Windows? Plan9? Big or little endian?", and so on) J. _______________________________________________ Scheme-reports mailing list [email protected] http://lists.scheme-reports.org/cgi-bin/mailman/listinfo/scheme-reports
