A function has ONE parameter and ONE return value. The trick is that these parameters and returned values may be tuples or functions themselves. So we can hav

A function has ONE parameter and ONE return value. The trick is that these parameters and returned values may be tuples or functions themselves. So we can have a function which takes a single parameter which is a tuple : function_name :: (Param1Type, Param2Type) -> ReturnType Or we can have a function which takes a single parameter and returns another function: function_name :: Param1Type -> (Param2Type -> ReturnType) Using implied operator precedence, the later is written: function_name :: Param1Type -> Param2Type -> ReturnType And has to be distinguished from a function which takes a function as parameter: function_name :: (Param1Type -> Param2Type) -> ReturnType