Hi, data TisanInteger = Tisan Integer instance Eq (*Tisan Integer*) where (Tisan v) == (Tisan v') = v == v' I think the part in red is the error: you should write *TisanInteger* instead (with no space between Tisan and Integer): This is because there you should put the name of the data, not its definition. Best, Ut Il giorno mer 22 apr 2020 alle ore 20:11 Alexander Chen < alexander@chenjia.nl> ha scritto:

Hi,

*data TisanInteger = Tisan Integer*

*instance Eq (Tisan Integer) where (Tisan v) == (Tisan v') = v == v'*

*prelude>* *Instance_testen.hs:7:14: error:* * Not in scope: type constructor or class ‘Tisan’* * A data constructor of that name is in scope; did you mean DataKinds?* * |* *7 | instance Eq (Tisan Integer) where (Tisan v) == (Tisan v') = v == v' | ^^^^^* *[1 of 1] Compiling Main ( Instance_testen.hs, interpreted )* *Failed, no modules loaded.*

what am i doing wrong?

best,

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