Norman | - Is there anything published about the implementation of GHCi? | Or perhaps something on the Developers' Wiki that explains how it works? If you mean the details of bytecode compilation and the bytecode interpreter, I'm really not sure that there is. That's bad; there should be. I'm ccing Simon M in case he knows of something. | - What is the best paper (or papers) to consult on the semantics | of GHC core? Many of these papers http://research.microsoft.com/en-us/um/people/simonpj/papers/ext-f/ give syntax, static semantics, and operational semantics of Core. Moreover, Richard Eisenberg has developed a specification of the Real Core in GHC, kept in the source tree in docs/core-spec I enclose a typeset version. Sadly it doesn't include operational semantics, but I don't think that'd be hard to add, would it Richard? The papers on the above link give several versions of the operational semantics, which is largely straightforward. Simon