<html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#FFFFFF" text="#000000"> <div class="moz-cite-prefix">_array produces a ctype, not an actual array itself. To get an array you can create one with malloc or you can call a C function through the ffi. If you use malloc then you get back a generic #<cpointer> type which you can convert to an array using ptr-ref as per the docs: "Since an array is treated like a struct, casting a pointer type to an array type does not work. Instead, use ptr-ref with a pointer, an array type constructed with _array, and index 0 to convert a pointer to a Racket representation that works with array-ref and array-set!." -> (require ffi/unsafe) -> (define t (_array _int 3)) -> (define x (malloc t)) -> (define a (ptr-ref x t 0)) -> a #<array> -> (array? a) #t -> (array-ref a 1) 1056768 -> (array-set! a 1 12) -> (array-ref a 1) 12 Or as an ffi function type (-> _int -> (_array _int 3)), although I didn't test that. On 12/13/2012 11:48 PM, 刘海宽 wrote: </div> <blockquote cite="mid:tencent_44AE6DB42AC19FA5775E3150@qq.com" type="cite">in the reference, I see the _array function, but I don't understand well, when i try to do, always output errors, can anyone give me an example? here is my test in REPL: racket@> (_array _int 3) #<ctype> racket@> (array? (_array _int 3))    ; why? #f racket@> <fieldset class="mimeAttachmentHeader"></fieldset> <pre wrap="">____________________ Racket Users list: <a class="moz-txt-link-freetext" href="http://lists.racket-lang.org/users">http://lists.racket-lang.org/users</a> </pre> </blockquote> </body> </html>