syntax-case bug

[leppie]

Ikarus Scheme version 0.0.3+ (revision 1452, build 2008-04-20)
Copyright (c) 2006-2008 Abdulaziz Ghuloum

> (syntax-case '(lambda (x) x) (lambda) [(lambda (x) y) #'x])
Unhandled exception
 Condition components:
   1. &assertion
   2. &who: stx-mark*
   3. &message: "not a struct of required type"
   4. &irritants: (lambda #<stx rtd>)

> (syntax-case '(lambda (x) x) (lambda) [(lambda (x) y) 'x])
Unhandled exception
 Condition components:
   1. &assertion
   2. &who: stx-mark*
   3. &message: "not a struct of required type"
   4. &irritants: (lambda #<stx rtd>)

Petite Chez Scheme Version 7.4
Copyright (c) 1985-2007 Cadence Research Systems

> (syntax-case '(lambda (x) x) (lambda) [(lambda (x) y) #'x])
x
> (syntax-case '(lambda (x) x) (lambda) [(lambda (x) y) 'x])
x

Cheers

leppie

[Abdulaziz Ghuloum (aghuloum)]

Definitely a bug. Will fix. Thanks.

[Abdulaziz Ghuloum (aghuloum)]

The bug is actually in (identifier? 'sym) returning #t instead of #f.

[leppie (leppie)]

Here it the simplest case:

(syntax-case 'f (f) [f f])

[leppie (leppie)]

Oops, make that:

(syntax-case 'f (f) [f 'f])

[Abdulaziz Ghuloum (aghuloum)]

Now I fixed it (in revision 1453) BUT the examples you cited do not match because the lambda symbol is not an identifier and so it cannot be free-identifier=? with the lambda identifier listed in the literals lists. So, now you get:

Ikarus Scheme version 0.0.3+ (revision 1453, build 2008-04-28)
Copyright (c) 2006-2008 Abdulaziz Ghuloum

> (syntax-case '(lambda (x) x) (lambda) [(lambda (x) y) #'x])
Unhandled exception
 Condition components:
   1. &message: "invalid syntax"
   2. &syntax:
       form: (lambda (x) x)
       subform: #f
> (syntax-case '(lambda (x) x) (lambda) [(lambda (x) y) #'x] [_ 'nop!])
nop!
>

[leppie (leppie)]

So if I understand you correctly syntax-case cannot match the lambda (or any other symbols) unless the input is syntax?

[Abdulaziz Ghuloum (aghuloum)]

On Apr 28, 2008, at 3:50 PM, leppie wrote:
> So if I understand you correctly syntax-case cannot match the
> lambda (or
> any other symbols) unless the input is syntax?

To match a symbol as a literal, you need a specific guard like:

 > (syntax-case '(lambda (x) foo) ()
     [(kwd (x) y) (eq? #'kwd 'lambda)
      (list #'x #'y)])
(x foo)

[which works in ikarus, chez, and larceny]

Aziz,,,