At Tue, 23 Jul 2013 14:24:10 -0400, John Clements wrote: > Welcome to DrRacket, version 5.3.5.900 [3m]. > Language: racket; memory limit: 512 MB. > expanded: '(let-values (((x) '19)) (let-values () x)) > x-binding: .#<syntax:5:12 x> > x-use: .#<syntax:8:7 x> > free-id=? #t > bound-id=? #t > > > > In particular, this result--that the binding instance of 'x' and the > macro-introduced use of 'x' are *bound*-identifier=?--surprises me.
It's because you're looking at a fully expanded form... > To take a step back, my low-level understanding All correct, as far as I can tell, at the point at which the `getx' macro has just been expanded. But the next step is to expand/parse `x', which doesn't just leave the `x' as it was; the `x' expands to an identifier for the binding of `x'. In MtWT, see the 7th rule for `expand', which says expand[[id, xi, Sigma]] = <id_new, Sigma> where (Var id_new) = xi(resolve[[id, Sigma]]) The `x' that you have in mind is `id', but the `x' you're checking with `build-identifier=?' is `id_new'. ____________________ Racket Users list: http://lists.racket-lang.org/users
