Why doesn't this type declaration work?

Question

I'm trying to create a 'Person' type where each person has a sex and a name.

data Sex = Sex Char deriving Show

male   = Sex 'M'
female = Sex 'F'

data Name   = Name [Char]      deriving Show

data Person = Person { 
    Sex    :: Sex,
    Name   :: Name
} deriving (Show)

When I try to load this in ghci I just get the unhelpful error parse error on input 'Sex'

What am I doing wrong here?

Answer 1

The problem lies in your usage of upper case inside the record syntax. The code should look like:

data Person = Person { sex :: Sex, name :: Name }...

Trying that, the code seems to at least compile. Since "sex" and "name" are not types (while "Sex" and "Name" are), you cannot make the first letters upper case.