Rodrigo wrote:
type Scenario = (String, String, [Step]) type Step = (String, Scenario, String, String, String)
Recursive types are not supported by type-declarations. use data declarations instead: data Scenario = Scenario String String [Step] data Step = Step String Scenario String String String As a general rule, data declaration are more approbiate then type declarations with a tuple on the right-hand-side. a type declarations introduces a type synonym, that is, a new name for an existing type. Data declarations introduce a new type. most of the time, you want new types, not more names for the same types. different names for the same thing lead to confusion, but different things for different usages lead to static type safety. (But this is only a general rule, and sometimes you want exactly the behaviour of type synonyms, of course) Tillmann