Using `mylang/semantics` will work as long as you have the `mylang` collection installed, which is necessary for `#lang` to work anyway.
In cases when it is sensible to use your new language without the custom reader (e.g. for languages which don't have a custom reader), it is often pleasant to have the name of the language be the same regardless of whether the programmer writes `#lang mylang` or `(module some-module mylang body ...)`. This can be accomplished by putting the contents of your current "semantics.rkt" in "main.rkt" and then giving "main.rkt" a reader submodule that refers to the enclosing module, e.g. `(module reader syntax/module-reader mylang)`. Whether or not this makes sense depends, of course, on the particulars of the language you're defining. -Philip On Sun, Oct 1, 2017 at 2:50 PM, Jordan Johnson <j...@fellowhuman.com> wrote: > Hi all, > > I’ve been putting together a little language to learn more about how the > Racket #lang ecosystem works, and I’m hung up on bundling up the language > as a collection. I’m not sure I correctly understand the point where the > reader attaches to the macros that specify how to expand the language > forms, and I want to check. > > So, say I have a file *semantics.rkt* (in *mylang/*, the main dir of the > collection) defining the macros that make up the language, and a reader > *lang/reader.rkt* (in the same dir): > > #lang s-exp syntax/module-reader > "../semantics.rkt" > #:read my-read > #:read-syntax my-read-syntax > > (require "lang/parser.rkt" syntax/strip-context) > > ;; ...simple defs of my-read and my-read-syntax... > > > This much works. My question is how to attach the *semantics.rkt* file to > my reader code correctly if I don’t use *syntax/module-reader*. If that’s > not clear enough, a more detailed description of the problem follows. > > Following the “Installing a Language” section in the Racket Guide, I > moved this reader code into a *main.rkt* file in the main dir of the > collection (call it *mylang/*): > > (module reader racket > (require "lang/parser.rkt" syntax/strip-context) > > (provide (rename-out [my-read read] > [my-read-syntax read-syntax])) > > (define (my-read in) (syntax->datum (my-read-syntax #f in))) > > (define (my-read-syntax src in) > (with-syntax ([(program-part ...) (parse-program-file src in)]) > (strip-context > #'(module IGNORE "semantics.rkt" > program-part ...))))) > > > I can then write > #lang mylang > in another file, and it works as expected *iff the file I’m loading is in > the mylang/ directory as well*, failing otherwise with an error like this: > > /path/to/mylang/main.rkt:17:24: cannot open module file > module path: #<path:/tmp/semantics.rkt> > path: /tmp/semantics.rkt > > > The module language spec I’ve highlighted in red seems brittle; because > Racket’s looking for *semantics.rkt* in the directory of the file > containing *#lang mylang* and not *mylang/*, I’ve been assuming that’s > where the problem is. Correct me if I’m wrong in this understanding: the > #'(module ...) is effectively replacing the body of whatever program is > written in *#lang mylang*, so the path-string "semantics.rkt" must be > interpreted relative to that program’s source file. > > Anyway, the solution I found is to replace "semantics.rkt" with > mylang/semantics, but that seems like it might be brittle as well; is that > the right way, though? If not, how should I be specifying the connection to > the macros? > > Thanks, > Jordan > > -- > 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. > -- 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.
