#lang racket
(provide interp-prim0 interp-prim1)

;; Op0 -> Value
(define (interp-prim0 op)
  (match op
    ['read-byte (read-byte)]
    ['peek-byte (peek-byte)]
    ['void      (void)]))

;; Op1 Value -> Value { raises 'err }
(define (interp-prim1 op v)
  (match (list op v)
    [(list 'add1 (? integer?))            (add1 v)]
    [(list 'sub1 (? integer?))            (sub1 v)]
    [(list 'zero? (? integer?))           (zero? v)]
    [(list 'char? v)                      (char? v)]
    [(list 'integer->char (? codepoint?)) (integer->char v)]
    [(list 'char->integer (? char?))      (char->integer v)]
    [(list 'write-byte    (? byte?))      (write-byte v)]
    [(list 'eof-object? v)                (eof-object? v)]
    [_ (raise 'err)]))

;; Any -> Boolean
(define (codepoint? v)
  (and (integer? v)
       (or (<= 0 v 55295)
           (<= 57344 v 1114111))))