Extending a datatype in Haskell

Question

Haskell newbie here.

I wrote an evaluator for a minimal assembly-like language.

Now, I want to extend that language to support some syntactic sugar which,

Answer 1

Syntactic sugar is usually handled by a parser; you'd extend (not in the sense of OO inheritance) the parser to detect the new constructs and translate them to the kind of structures that your evaluator can handle.