David McBride wrote:
Why not have:
data Question = Question { questionName :: Name , questionText :: QuestionText , questionType :: QuestionType , answerFunc :: (String -> AnswerType) , correctAnswer :: Maybe AnswerType , options :: Maybe [Option AnswerType] } deriving (Show)
data AnswerType = AnsD Double | AnsS String | AnsI Integer deriving (Show, Read)
Then, I'd personally make another change, why would you have a flat structure with a questionType and then optional correctAnswer and options fields? There's no type safety in that. I'd try:
data Answer = StraightAnswer (String -> AnswerType) | MultipleChoice AnswerType [Option AnswerType]
data Question = Question { questionName :: Name , questionText :: QuestionText , answerFunc :: (String -> AnswerType) , answer :: Answer } deriving (Show)
If you are storing answers as string, just store them as "AnsD 5.589", "AnsS \"Constantiople\"". Then with the read instance you can go:
let answer = read x :: AnswerType
Thank you very much for the reply which is eye-opening. But I do have to spend time implementing your revised schema in the prior question handling functions to get my head around it (-: Best, Alia