[Haskell-cafe] Comparison between fields of each record

[Jeon-Young Kang]

Dear All.

I'd like to compare fields of each record.

here is my record.

data Person = Person {name:: String, age:: Int } deriving(Show)

data Relations = Friend | Older | Younger

class Comparison a where

    compare:: a -> a -> Relations

instance Comparison Person where

    compare Person a b Person a b

         | b1 == b2 = Friend

         | b1 > b2 = Older

         | b1 < b2 = Younger

How can I fit it?

Sincerely,

 

Jeon-Young Kang

[Francesco Ariis]

Hello Jeon-Young, I attach a version that compiles. Keep in mind that

compare (Person x y) (Person q w) -- this is legal

compare Person x y Person q w -- "space" takes precedence over everything,
-- so this function has 6 arguments
-- instead of the expected 2!


λ> Main.compare (Person "cdsac" 1) (Person "cdscasd" 20)
Younger

[Jeon-Young Kang]

Thank you so much :) 

--

Department of Geography

State University of New York at Buffalo

jyka...@gmail.com

 

Jeon-Young Kang