Hello. I have a problem around how to use syntax-case.
Here's a situation.
I'm using SRFI-25, the array library. It is useful; however, it doesn't
provide something like "copy-array". I would not like to use something
"destructive", therefor I would like to make a copy of an array I defined.
I noticed I could make a copy if I use "array" function provided there.
Here is its format:
(array shape obj ...)
I mean, in order to make a copy of an array, the idea must be
(array (array-shape the-original) obj ...)
;however, I wondered how I should express "obj ..." part. The supplement of
SRFI25, or arlib.scm, provides array->list function, so I noticed I've got
to use a macro like this in the Common Lisp style.
(defmacro copy-array (arr)
`(array (array-shape arr) ,@(array->list arr)))
At first, I checked Racket reference and I tried (require
compatibility/defmacro).
> (require srfi/25 racket/include compatibility/defmacro)
> (include "arlib.scm")
> (define-macro (copy-array arr)
`(array (array-shape arr) ,@(array->list arr)))
> (define a (array (shape 0 3 0 3) 1 2 3 4 5 6 7 8 9))
> (define b (copy-array a))
. . array->list: undefined;
cannot reference an identifier before its definition
phase: 1
explanation: cannot access the run-time definition
Strangely, even though I'd included "arlib.scm", the interpreter said
array->list was undefined.
So it might be the time(actually the first time to me) to use syntax-case.
Through some basic tutorials around syntax-case, the syntax-case macro
equivalent to the macro written in Common Lisp style stated above must be
something like this, I believe:
(define-syntax copy-array
(lambda (stx)
(syntax-case stx ()
((_ arr)
#`(array (array-shape arr) #,@(array->list (syntax->datum
#'arr)))))))
I tried:
> (define b (copy-array a))
. . array->list: undefined;
cannot reference an identifier before its definition
phase: 1
explanation: cannot access the run-time definition
array->list is "undefined" again.
What happens in the syntax-case here?
Thanx.
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