Cannot specify an ellipsis for syntax-rules #706

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2023-06-12T13:22:57Z

Zambito1 commented

2023-06-12 13:22:57 +00:00

(Migrated from github.com)

In R7RS, syntax-rules has an optional extra argument to specify the term to use for the ellipsis. https://index.scheme.org/filterset/r7rs_small/%28scheme%2520base%29/syntax-rules

This does not seem to be handled correctly by Gerbil.

$ gxi --lang r7rs
R7RS Scheme in Gerbil v0.17 on Gambit v4.9.3
> (import (scheme base))
> (define-syntax foo (syntax-rules () ((_ x) (+ x 1))))
> (foo 5)
6
> (define-syntax foo (syntax-rules ::: () ((_ x :::) (+ x ::: 1))))
*** ERROR IN ##main -- Syntax Error
*** ERROR IN (stdin)@4.20
--- Syntax Error: Bad syntax
... form:   (syntax-rules ::: () ((_ x :::) (+ x ::: 1)))
> 
*** EOF again to exit
$ chibi-scheme -R
> (define-syntax foo (syntax-rules () ((_ x) (+ x 1))))
> (foo 5)
6
> (define-syntax foo (syntax-rules ::: () ((_ x :::) (+ x ::: 1))))
> (foo 1 2 3 4)
11

In R7RS, `syntax-rules` has an optional extra argument to specify the term to use for the ellipsis. https://index.scheme.org/filterset/r7rs_small/%28scheme%2520base%29/syntax-rules This does not seem to be handled correctly by Gerbil. ```scheme $ gxi --lang r7rs R7RS Scheme in Gerbil v0.17 on Gambit v4.9.3 > (import (scheme base)) > (define-syntax foo (syntax-rules () ((_ x) (+ x 1)))) > (foo 5) 6 > (define-syntax foo (syntax-rules ::: () ((_ x :::) (+ x ::: 1)))) *** ERROR IN ##main -- Syntax Error *** ERROR IN (stdin)@4.20 --- Syntax Error: Bad syntax ... form: (syntax-rules ::: () ((_ x :::) (+ x ::: 1))) > *** EOF again to exit $ chibi-scheme -R > (define-syntax foo (syntax-rules () ((_ x) (+ x 1)))) > (foo 5) 6 > (define-syntax foo (syntax-rules ::: () ((_ x :::) (+ x ::: 1)))) > (foo 1 2 3 4) 11 ```

vyzo commented

2023-06-12 13:54:34 +00:00

(Migrated from github.com)

Yeah, iirc it was in my todo list but never got around implementing it.

Care for a pr? It shouldnt be all that hard.

We can also just document it as a limitation, waiting for the next hacker to be annoyed enough to fix it ;)

Yeah, iirc it was in my todo list but never got around implementing it. Care for a pr? It shouldnt be all that hard. We can also just document it as a limitation, waiting for the next hacker to be annoyed enough to fix it ;)

vyzo commented

2023-06-12 13:56:23 +00:00

(Migrated from github.com)

Ah btw, ::: is a keyword!

So you should |:::| or use an identifier.

Ah btw, `:::` is a keyword! So you should `|:::|` or use an identifier.

iacore commented

2024-03-08 14:35:36 +00:00

(Migrated from github.com)

I think this is not a bug?

vyzo commented

2024-03-08 14:37:29 +00:00

(Migrated from github.com)

Using a keyword is wrong, but still, custom ellipsis is not implemented atm. It is not a bug per se, more of an omission, that is readily fixable.

I will try to fix it for v0.18.2.

Using a keyword is wrong, but still, custom ellipsis is not implemented atm. It is not a bug per se, more of an omission, that is readily fixable. I will try to fix it for v0.18.2.

vyzo commented

2024-03-08 14:37:52 +00:00

(Migrated from github.com)

You can also give it a go if you want!

iacore commented

2024-03-08 14:57:55 +00:00

(Migrated from github.com)

I found a way to workaround this

❯ rlwrap gerbil
Gerbil v0.18.1 on Gambit v4.9.5-78-g8b18ab69
> (define-syntax foo (syntax-rules () ((_ x . xs) (+ x 1 . xs))))
> (foo 1)
2
> (foo 2)
3
>

I found a way to workaround this ``` ❯ rlwrap gerbil Gerbil v0.18.1 on Gambit v4.9.5-78-g8b18ab69 > (define-syntax foo (syntax-rules () ((_ x . xs) (+ x 1 . xs)))) > (foo 1) 2 > (foo 2) 3 > ```

iacore commented

2024-03-08 15:03:01 +00:00

(Migrated from github.com)

You can also give it a go if you want!

I looked at the code in core.scm and I don't know what I was looking at.

it seems to be something like this:

(define-syntax ... (syntax-rules () (_ (unquote-splicing xs))))

> You can also give it a go if you want! I looked at the code in `core.scm` and I don't know what I was looking at. it seems to be something like this: ``` (define-syntax ... (syntax-rules () (_ (unquote-splicing xs)))) ```

vyzo commented

2024-03-08 15:12:13 +00:00

(Migrated from github.com)

It needs to be supported by syntax-case, it is in src/gerbil/expander/stxcase.ss

iacore commented

2024-03-08 15:25:34 +00:00

(Migrated from github.com)

It seems like i just need to replace ellipsis? with a custom one. Is the symbol lexical in Gambit? Can I just replace that somehow?

It seems like i just need to replace `ellipsis?` with a custom one. Is the symbol lexical in Gambit? Can I just replace that somehow?

vyzo commented

2024-03-08 15:29:43 +00:00

(Migrated from github.com)

yes, it is simple.

vyzo commented

2024-03-08 15:31:57 +00:00

(Migrated from github.com)

Add an optional argument for the ellipsis? procedure, defaulting to the real ellipsis?.

You will the have to change the syntax-rules macro a bit to recongize and pass the parameter as free-identifier=? the user's identifier.

Add an optional argument for the ellipsis? procedure, defaulting to the real ellipsis?. You will the have to change the syntax-rules macro a bit to recongize and pass the parameter as free-identifier=? the user's identifier.

iacore commented

2024-03-08 15:36:02 +00:00

(Migrated from github.com)

is it possible to nest ellipsis somehow?

for example:

(syntax-rules ...a () ((_ ...a)
(syntax-rules ...b () ((_ ...b)
(test ...a)
))
))

is it possible to nest ellipsis somehow? for example: ``` (syntax-rules ...a () ((_ ...a) (syntax-rules ...b () ((_ ...b) (test ...a) )) )) ```

vyzo commented

2024-03-08 15:38:31 +00:00

(Migrated from github.com)

yes, (... ...)

yes, `(... ...)`

iacore commented

2024-03-08 15:45:38 +00:00

(Migrated from github.com)

I don't know enough about Gerbil to patch this. Is it possible to rewrite the body before it is sent to src/gerbil/expander/stxcase.ss?

I don't know enough about Gerbil to patch this. Is it possible to rewrite the body before it is sent to `src/gerbil/expander/stxcase.ss`?

vyzo commented

2024-03-08 15:48:17 +00:00

(Migrated from github.com)

nah, no need. I will add it to my todo list.

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mighty-gerbils/gerbil#706

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