Hey! On Mon 18 Nov 2019 16:10, Mark H Weaver <m...@netris.org> writes:
> Andy Wingo <wi...@pobox.com> writes: > >> R7RS defines a lexical feature called "datum labels"; see section 2.4 in >> the report. An example would be: >> >> #0=(a b c . #0#) >> >> Guile's reader doesn't support this feature and it's not clear if we >> should, in general. > > FYI, I already implemented R7RS datum labels on the 'r7rs-wip' branch > (not to be confused with your new 'wip-r7rs' branch): > > > https://git.savannah.gnu.org/cgit/guile.git/commit/?h=r7rs-wip&id=92408ac20e921583b8e4ee26463dc5805ef01153 > > It depends on the preceding commit on the same branch: > > > https://git.savannah.gnu.org/cgit/guile.git/commit/?h=r7rs-wip&id=f687871eceb94bded109569880e696d8862d84fd > > There was also a later commit on that branch that enabled compilation of > cyclic literals, but it's no longer applicable to the 'master' branch. Neat! I had entirely forgotten about this branch. >> Note, datum literals appear to be incompatible with array literals. > > Can you elaborate on why you believe they're incompatible? I haven't > looked closely in a while, but I didn't see any incompatibility when I > implemented this before. Datum labels have '#' or '=' after the > numeral, and I'm not aware of any Guile array syntax that does. I was wrong. Thanks for the correction! > I'm also a bit puzzled why you're apparently planning to rewrite > everything I already did on the 'r7rs-wip' branch. The main issue on > that branch is that the implementation of *writing* cyclic data turned > out to be a mess, but it could be removed or replaced without affecting > much else. I had totally forgotten about it. I am surprised no one on #guile brought it up either when I was discussing this work! As you can see, the the writing implementation currently uses srfi-38. For what it's worth, I do not have future plans to work on R7RS -- I just wanted --r7rs so that I could have an easy way to benchmark against other Scheme systems. A strange reason, admittedly! Andy
