at http://www.haskell.org/onlinereport/exps.html on figure Figure 4 (Semantics of Case Expressions, Part 2) one can see: (m) case v of { K { f1 = p1 , f2 = p2 , ... } -> e ; _ -

e' } = case e' of { y -> case v of { K { f1 = p1 } -> case v of { K { f2 = p2 , ... } -> e ; _ -> y }; _ -> y }} where f1, f2, ... are fields of constructor K; y is a new variable

(In Figures 3.1--3.2: e, e' and ei are expressions; g and gi are boolean-valued expressions; p and pi are patterns; v, x, and xi are variables; K and K' are algebraic datatype (data) constructors (including tuple constructors); and N is a newtype constructor.) I'm totally confused with this identity. Especialy with " = case e'". Can anyone explain a little what does this rule stand, please? It is better to see some example. Respect, Michael