Implement integer->char and char->integer

scm/inc/compiler.scm

     (case (primcall-op x)
       ((add1)
        (emit-expr (primcall-operand1 x))
        (emit "addl $~a, %eax" (immediate-rep 1)))))))
        (emit "addl $~a, %eax" (immediate-rep 1)))
       ((integer->char)
        (emit-expr (primcall-operand1 x))
        (emit "shl $6, %eax")
        (emit "xorl $15, %eax"))
       ((char->integer)
        (emit-expr (primcall-operand1 x))
        (emit "shrl $6, %eax"))))))
(define (compile-program x)
  (display ".globl scheme_entry\n\n")
  (emit-expr x)
  (emit "ret"))
(compile-program '(add1 41))
(compile-program '(char->integer #\y))