Hello, Out of curiosity, I tried user defined kinds. wojtek@biuro:~/src/he $ cat udk.hs data kind Nat = Z | S Nat wojtek@biuro:~/src/he $ jhc -fuser-kinds udk.hs jhc -fuser-kinds udk.hs jhc 0.8.2 (mydniquipepo-32) Finding Dependencies... Using Ho Cache: '/home/wojtek/.jhc/cache' udk.hs:2 - Error: Illegal data/newtype declaration What am I doing wrong? -- Kind regards, Wojtek Narczyński