On Jul 10, 2014, at 12:56 PM, Alexander D. Knauth <alexan...@knauth.org> wrote:
> Ok now it does this: > > #lang afl at-exp racket/base > (map #λ@+[% 1] '(1 2 3)) ; @+: unbound identifier in module in: @+ After doing the read-syntax/recursive thing now this first error goes away (I have no Idea why), but the other ones are still the same. > #lang at-exp afl racket/base ; different order > (map #λ@+[% 1] '(1 2 3)) ; ‘(2 3 4) > > #lang afl at-exp racket/base ; original order > @#λ(+ % 1)[1] ; 2 > > #lang at-exp afl racket/base ; different order > @#λ(+ % 1)[1] ; read: bad syntax `#λ’ This error is still there though. Does at-exp use read-syntax/recursive? Would that fix this? I don’t see why it would, but then I don’t see why it would fix the other error either. > Is there any way to get around this? > > On Jul 10, 2014, at 11:51 AM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > >> 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 ____________________ Racket Users list: http://lists.racket-lang.org/users