Hi all, I have the following data types: type Id = String type Action = String type State = String type Response = String data Scenario = Scenario Description [Step] data Step = Step Id Scenario Action State Response So, there is a mutual recursion between Scenario and Step. Now, consider the following function: xmlScenario2Scenario :: XmlScenario -> Scenario xmlScenario2Scenario (XmlScenario description steps) = Scenario description [xmlStep2Step x | x <-steps] How can I send "scenario" as an argument for xmlStep2Step? I've tried let and where but I get in a loop. Thanks a lot, Rodrigo. ----------------------------------- Rodrigo Bonifácio de Almeida Universidade Católica de Brasília - Grupo de Engenharia de Software - JavaComBr (www.ucb.br/java)