Hello Johannes, Thursday, February 09, 2006, 1:43:38 PM, you wrote: JW> With Data.Generics, we can get an object's type, constructor and fields. really, SYB way to metaprogramming is just to encode information about type in the datastructure. you can do somethiong in this fashion just by coupling together value and functions that is able to show, map and otherwise process this value. due to simple changes in the compiler, functions that translate value into such self-describing structure, are generated automatically. but they can be written manually or by TH 9it was used before compiler was modified). so it is not exact compile-time vs dynamic inspection of metainformation, it's just a general datatype which hoilds all the metainformation about value and therefore can be inspected at run-time to dynamically decide what to do with that value in its current state, information coupled together with value, don't include that you want, but this can be changed. again, this change need to either change a compiler so that it can pack his information when converting "a->Dynamic", or you can write these data manually, or again TH can be used and you will be limited only by the volume of information, available for TH code. except for this, extensing SYB don't require any extensions to the language -- Best regards, Bulat mailto:bulatz@HotPOP.com