"Taesch, Luc" wrote:

do u isolate just the datatype, or a few related with, in a very small file (header like, i would say) or some basic accessor function with it ?

isnt it leading to massiv quantities of small files ?

Asuming you have some typed AST with many mutually recursive datatypes, I would keep them in one big file. This should be fine if the datatypes are simple (no "deriving" Read and Show etc.). For an AST you don't want accessor functions: the datatypes are the interface. For some datatypes you want to hide the datatype and provide a function based interface, this should be in the same file as the datatype. Usually there is also some kind of asumed hierarchy in datatypes, e.g. Int < List < FiniteMap, to determine where functions operating on multiple datatypes should be placed, but that's the same in OO. Jan