model.rkt

#lang racket/base
(require racket/date
         racket/contract
         racket/serialize)

(struct assignment (normal-weight optional-weight id due-secs eval-secs peer-secs questions) 
        #:prefab)
(struct question (normal-weight optional-weight prompt type)
        #:prefab)
(struct student (nickname firstname lastname email)
        #:prefab)
(struct answer (timestamp comments)
        #:prefab)
(struct answer:bool answer (value)
        #:prefab)
(struct answer:numeric answer (value)
        #:prefab)

(provide/contract
 [struct assignment
         ([normal-weight number?]
          [optional-weight number?]
          [id string?]
          [due-secs number?]
          [eval-secs number?]
          [peer-secs (or/c false/c number?)]
          [questions (listof question?)])]
 [struct question
         ([normal-weight number?]
          [optional-weight number?]
          [prompt string?]
          [type (or/c 'bool 'numeric)])]
 [struct answer
         ([timestamp exact-nonnegative-integer?]
          [comments string?])]
 [struct answer:bool
         ([timestamp exact-nonnegative-integer?]
          [comments string?]
          [value boolean?])]
 [struct answer:numeric
         ([timestamp exact-nonnegative-integer?]
          [comments string?]
          [value (between/c 0 1)])]
 [struct student
         ([nickname string?]
          [firstname string?]
          [lastname string?]
          [email string?])])