I think the problem may be in `at-exp`. If you change
pkgs/racket-pkgs/at-exp-lib/at-exp/lang/reader.rkt and replace the use of `at-readtable` with `(make-at-readtable)`, does that fix the problem? At Thu, 10 Jul 2014 11:30:18 -0400, "Alexander D. Knauth" wrote: > > On Jul 10, 2014, at 6:40 AM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > > > The readtable strategy works when <language> itself uses a > > readtable-based reader. The idea is that you install a mapping for `#λ` > > while leaving all the other mappings in place. If <language> uses a > > readtable-based reader, then it picks up your extension, otherwise it > > doesn't. > > > > I think a `#lang afl at-exp racket` combination should work fine: `afl` > > installs a handler for `#λ`, `at-exp` installs a handler for `@`, and > > `racket` uses `read-syntax` to see both extensions. > > Well for some reason it doesn’t: > #lang afl at-exp racket/base > (map #λ(+ % 1) '(1 2 3)) ; read: bad syntax `#λ’ > > But also for some reason this does: > #lang at-exp afl racket/base > (map #λ(+ % 1) '(1 2 3)) ; '(2 3 4) > (map #λ@+[% 1] ‘(1 2 3)) ; ‘(2 3 4) > By the way I only just got this to work yesterday by doing basically this but > for afl: > https://github.com/AlexKnauth/rackjure/commit/5fa266e672d529dde227ef216aaef157fa > 5c618c > > Also is there any way to get something like this to work?: > #lang afl at-exp racket/base > @#λ(+ % 1)[1] ; read: bad syntax `#λ' > > > Adding `#fn` support is a little trickier if you want to fall back to > > `#f` or `#false` when the character after `#f` (as determined by a > > peek) is not `n`. For that case, the readtable addition for `#f` should > > remember the old readtable, and then when it needs to fall back, it > > calls `read/recursive` with the saved readtable as the third argument. > > That way, immediate parsing of `#f...` uses the saved readtable without > > `afl` extensions, while parsing of sub-expressions will return to the > > current readtable that includes the `afl` extensions. > > Do you mean like this?: > (define lambda-readtable (current-readtable)) > (parameterize ([current-readtable orig-readtable]) > (read-syntax/recursive src in #f lambda-readtable)) > > > Documentation for the functions from a "<language>/lang/reader.rkt" is > > in section 1.3.18 of the Reference, which defines `#lang` (as being > > "like `#reader`, which is described in the same section). > > Ok I just found this in section 1.3.18: > The arity of the resulting procedure determines whether it accepts extra > source-location information: a read procedure accepts either one argument (an > input port) or five, and aread-syntax procedure accepts either two arguments > (a > name value and an input port) or six. In either case, the four optional > arguments are the reader’s module path (as a syntax object in read-syntax > mode) > followed by the line (positive exact integer or #f), column (non-negative > exact > integer or #f), and position (positive exact integer or #f) of the start of > the > #reader form. > > But maybe there should be a link or something to section 1.3.18 from sections > 17.2 and 17.3.1 of the Guide. > That would make it a lot easier to find it. > > > > > At Sat, 5 Jul 2014 13:33:27 -0400, "Alexander D. Knauth" wrote: > >> > >> If I have a meta-language like this: > >> #lang my-meta-lang <language> > >> And my-meta-lang is similar to at-exp in that it can accept any arbitrary > >> language with any arbitrary reader > >> (as long as it looks at the readtable), then how do I escape back to the > reader > >> specified by <language> > >> from inside a reader macro from my-meta-lang? > >> > >> What I’m trying to do is something like #lang afl <language> where afl > >> adds > >> rackjure-like anonymous function literals > >> to <language>. > >> > >> So to parse this: > >> #lang afl racket > >> #λ(+ % 1) > >> It would use the racket reader but wrap it to use the afl-readtable, which > >> includes dispatch-macros that would > >> read the (+ % 1) and parse the result into a lambda expression. > >> > >> But if <language> was something else, with a different reader, then how > could I > >> use that to read the (+ %1 1). > >> > >> For example if it was something like this: > >> #lang afl at-exp racket > >> #λ@+[% 1] > >> > >> There’s also another problem. If it was this: > >> #lang afl <language> > >> #f > >> Or this: > >> #lang afl <language> > >> #false > >> Or some other thing starting with f that means something to <language>, > >> Then it would see the #f and hope that it would turn out to be #fn. If it > >> doesn’t, then it uses the racket reader > >> (instead of the one provided by <language>) to read the #f or the #false. > >> > >> So back to my original question: How do I escape back to the reader > specified > >> by <language> > >> from inside a reader macro? > >> > >> By the way I can’t find anything in the docs about what the arguments to > >> the > >> read and read-syntax functions > >> provided by <language>/lang/reader.rkt are supposed to be or mean. > >> > >> > >> ____________________ > >> Racket Users list: > >> http://lists.racket-lang.org/users > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
