Hello Andrew, Saturday, January 28, 2006, 1:38:08 PM, you wrote: AS> def myeval(x, y, op) AS> x.send op, y AS> end AS> I had a feeling this sort of dynamic sending of messages AS> to objects at run time was impossible in Haskell, hence AS> my question. What I'm still unsure about is why this sort AS> of thing is impossible in Haskell. Is it a fair comment AS> to state that this sort of thing is impossible in Haskell AS> as a consequence of its static typing? Or could it be done AS> in a static typed language with more run time support? it's because Haskell is compiled laguage and in compiled program "a+b" represented just by asm instructions and don't had any link with the string "+". To have such link it's necessary to had run-time typing information, and current Haskell implementations has that in the module Data.Dynamics. but even this information in current state don't know anything about "+" and other operations, it is only informatio about types itself. so, the anser: that can be done, but there is no much need in it. on the other side, there is a huge area of "generic programming" techniques that is something like to run-time investigation of type structure, that is available in Ruby. using this one can, for example, traverse some complex data structure that uses hundreds of different types, and replace, say, only Int's with another values. Data.Dynamics is for such types of tasks AS> Despite being longer, overall I prefer the Haskell version AS> because it is faster and "safer" (in that a number of run AS> time errors in the Ruby version are caught at compile time AS> in the Haskell version). yes, and that is unvaluable for real-world large projects -- Best regards, Bulat mailto:bulatz@HotPOP.com