#lang racket

(require [for-syntax racket/stream])

(define-for-syntax (range n) (stream->list (in-range n)))

(define-syntax big-case-datum
  (lambda (ctx)
    (syntax-case ctx ()
      ((_ n)
       (with-syntax ([ra (datum->syntax ctx (range (syntax->datum #'n)))])
         #'(lambda (a) (case a
                   (ra 'in)
                   (else 'out))))))))

((big-case-datum 10) 2) ;; => 'in
((big-case-datum 10) 13) ;; => 'out