On Mon, May 2, 2016 at 7:34 PM, Matthew Butterick <m...@mbtype.com> wrote: >> On May 2, 2016, at 11:50 AM, Sam Tobin-Hochstadt <sa...@cs.indiana.edu> >> wrote: >>> >>> My initial statement was less precise than my second email. >>> `(syntax-local-introduce stx)` adds a single scope, using the >>> equivalent of `'flip` mode. That scope is "the current scope" for the >>> macro expansion step. > > I appreciate your more detailed explanation. > > The common thread in the Knauth/Butterick critique is that > `syntax-local-introduce` promises a result — syntax, locally introduced — but > in fact delivers a certain action — adding a scope — that will only achieve > the promised result if a certain other criterion is met (namely, a > context-free syntax object). This is not apparent from the docs (though I > will prepare a pull request to make it so).
I don't understand what the critique is supposed to be. Are you saying that the name is misleading? Or that it should do something different? Or just that the docs need clarifying? > Even with this clarification, some puzzling behavior awaits. For instance, > you are correct that using `(datum->syntax #f 'x)` makes my two original > examples work. But consider example #3 — where a subsequent local definition > will shadow the `syntax-local-introduce` identifier, without an error — and > example #4, which reverses the order of the two binding expressions, which > then triggers an ambiguous-binding error. What's going on here is the complexities of internal definition contexts, and the scopes that they add. In Example #3, there's an extra scope for the locally-defined x, which is applied to the x reference, meaning that it has one more scope that the introduced binding doesn't have, so the x matches it. Strangely, your Example #4 works the same as example #3, except in DrRacket, where it errors. Sam -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
