Haskell "parse error on input `=>' "


    first :: (a,b,c) -> a
    first (x, _, _) = x
    
    second :: (a,b,c) -> b
    second (_,y,_) = y
    
    third:: (a,b,c)-> c
    third (_,_,z) => z

I got error message from this piece of code.

    "parse error on input `=>'
    "

I cannot see any reason. Could anyone help me to point out?
thanks.

Haskell "parse error on input `=>' "
===



    first :: (a,b,c) -> a
    first (x, _, _) = x
    
    second :: (a,b,c) -> b
    second (_,y,_) = y
    
    third:: (a,b,c)-> c
    third (_,_,z) => z

I got error message from this piece of code.

    "parse error on input `=>'
    "

I cannot see any reason. Could anyone help me to point out?
thanks.
