Hi all, Lately I've found implicit parameters to be extremely usefull in many situations. The most simple and obvious is when you need to calculate some values that depend on specific parameters, in some context where these same parameters constant. There is no poblem if all the calculus are defined in the scope of those 'constant' parameters, but if you need to define functions outside their scope then you have to pass them as arguments, and sometimes that complicates type signatures. Now my question. I've end up in situations where I need to write something like --------- step :: Inst-> Train->Inst step inst train = changeInst deltaW deltaV inst where deltaW = someSemiConst1 with ?inst=inst; ?train train deltaV = someSemiConst2 with ?inst=inst; ?train train --------- Ok the problem is that both deltaV and deltaW are assigned some constants that implicitly depend on the arguments 'inst' and 'train'. Now imagine that someSemiConst1 = f n someSemiConst2 = g n for some n that also depends implicitly on 'inst' and 'train'. In this case 'n' would (could? haven't actually tried it) be calculated twice, one fro the first semiConst, another for the second. It would be nice to have something like with ?inst=inst; ?train train { deltaW = someSemiConst1 deltaV = someSemiConst2 } My solution was to define some function (deltaW, deltaV)=calculateDeltas with ?inst=inst; ?train=train And in this function I simple does (deltaW, deltaV)= (someSemiConst1, someSemiConst2) In case you're wondering, why not just call the 'step' function bounding it's context to 'inst' and 'train'. It doesn't makes much sense to me in this case, becouse the whole purpose of this function is to change a 'inst' acording to some 'train' (in fact it is beeing used in a foldl). How do you usually handle this situations? Is there an elegant solution for this? J.A.