[racket] how to create a ctype array

[刘海宽]

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@>

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