Re: [Haskell-beginners] Type constructors sharing a common field

Hi, On 2014-04-28 19:26, Lorenzo Tabacchini wrote:

Imagine the following data type:

data Person = Child { childAge :: Int, school :: School } | Adult { adultAge :: Int, job :: Job }

Both the alternatives share an "age" field, but in order to access it we are obliged to match all the constructors:

personAge :: Person -> Int personAge (Child {childAge = age}) = age personAge (Adult {adultAge = age}) = age Is there a way to define a common field in a data type (somehow like inheritance in the OOP world)?

Yes, there is: data Person = Child { personAge :: Int, school :: School } | Adult { personAge :: Int, job :: Job } No extension needed! Thomas H