orchsyn

Copperbox revision 2709.

I've got a bit stuck with Orchsyn due to building code within a monad. The do-notation seems to make the embedded language a statement language, but this means I don't know what types the opcode built-ins should be (so they can account for arity of the result).

As an alternative, I've be experimenting using the tagless-final style to embed an expression language with sharing within normal Haskell (not the do-notation). I'm quite pleased with the results - I've embedded ref cells, lambda and apply, sharing let, if-the-else and primitive apply (for calling built-ins). The only problem is an expression language will need a real compiler - the abstract syntax is too far from Csound's imperative language to just pretty print to Csound.

This commit stores a series of expression languages (adding more features) as I don't want to lose them.