Could (define-syntax (name stx) ...) be brought back?

Thanks Abdulaziz Ghuloum, that solved my question.

I think the below works to make it so the same define-syntax disallows or allows the procedure-making define-syntax with formals -style depending on whether (ikarus) is in the environment. In psyntax.expander.ss, change parse-define-syntax to be:

  (define parse-define-syntax
    (lambda (x)
      (syntax-match x ()
        ((_ id val) (id? id) (values id val))
        ((_ (id . args) e e* ...)
         (or (and (member '(ikarus) (map library-name ((imp-collector))))
                  (id? id))
             (stx-error x "define-syntax with formals is invalid syntax in R6RS"))
         (values id (cons* (bless 'lambda) args e e*))))))

This seems to work:

$ cat ./ds-r6.ss
#! /home/d/bin/ikarus --r6rs-script
(import #;(ikarus) (rnrs))
(define-syntax (s stx)
  (syntax-case stx ()
    [(_ x) #'(begin (display x) (newline))]))
(s 'foo)

$ ikarus --r6rs-script ./ds-r6.ss
Unhandled exception:
 Condition components:
   1. &error
   2. &who: expander
   3. &message: "define-syntax with formals is invalid syntax in R6RS"
   4. &irritants: ((define-syntax (s stx) (syntax-case stx () ((_ x) #'(begin (display x) (newline))))))

# uncomment the import of (ikarus) and it's valid:

$ cat ./ds-r6.ss
(import (ikarus) (rnrs))
(define-syntax (s stx)
  (syntax-case stx ()
    [(_ x) #'(begin (display x) (newline))]))
(s 'foo)

$ ikarus --r6rs-script ./ds-r6.ss
foo

Similarly:

Ikarus Scheme version 0.0.1
Copyright (c) 2006-2007 Abdulaziz Ghuloum

> (expand '(let () (define-syntax (fail stx) #f) (fail))
                 (environment '(rnrs)))
Unhandled exception
 Condition components:
   1. &error
   2. &who: expander
   3. &message: "define-syntax with formals is invalid syntax in R6RS"
   4. &irritants: ((define-syntax (fail stx) #f))
>
> (expand '(let () (define-syntax (fail stx) #f) (fail))
                 (environment '(rnrs) '(ikarus)))
((case-lambda (() '#f)))
()

Actually make that:

  (define parse-define-syntax
    (lambda (x)
      (syntax-match x ()
        ((_ id val) (id? id) (values id val))
        ((_ (id . args) e e* ...)
         (and (or (member '(ikarus) (map library-name ((imp-collector))))
                  (stx-error x "define-syntax with formals is invalid syntax in R6RS"))
              (id? id))
         (values id (cons* (bless 'lambda) args e e*))))))

Unfortunately, this does not work in general. There are many cases where it breaks but I'll just mention 2.

Case 1:

#!/usr/bin/env scheme-script
(import (rnrs) (except (ikarus) define-syntax))
(define-syntax (foo x) 12) ;;; shouldn't this signal an error?
(foo)

Case 2:

(library (A)
  (export define-syntax)
  (import (ikarus)))

#!/usr/bin/env scheme-script
(import (A))
(define-syntax (foo x) 12) ;;; shouldn't this succeed?
(foo)

The problem here is that you want one identifier to denote two different things. If you have a single identifier (define-syntax), then you have no way of deciding which behavior to perform when you find that identifier. If you have two different identifiers and both are called define-syntax, then you get a conflict if you import both.

Duh, right. Oh well.

If, say, Dybvig, Clinger, and Flatt all agreed to support (define-syntax (name arg) ...)
would you then reconsider?

/Jens Axel,
(define-syntax (name stx) ...) is in my fingers,
not to mention all my code

On Dec 28, 2007, at 6:22 PM, Jens Axel Søgaard wrote:

> If, say, Dybvig, Clinger, and Flatt all agreed to support (define-
> syntax (name arg) ...)
> would you then reconsider?

Of course. Are you collecting signatures?

Abdulaziz Ghuloum skrev:
> Question #18207 on Ikarus Scheme changed:
> https://answers.launchpad.net/ikarus/+question/18207
>
> Abdulaziz Ghuloum posted a new comment:
>
> On Dec 28, 2007, at 6:22 PM, Jens Axel Søgaard wrote:
>
>> If, say, Dybvig, Clinger, and Flatt all agreed to support (define-
>> syntax (name arg) ...)
>> would you then reconsider?
>
> Of course. Are you collecting signatures?

I will now :-)

/Jens Axel