The overall objective of this assignment is to fully understand the notions of…

The overall objective of this assignment is to fully understand the notions of
lexing,
parsing,
scoping,
binding,
environments and closures,
by implementing an interpreter for a subset of Haskell.
No individual function requires more than 15-25 lines, so if you're answer is longer, you can be sure that you need to rethink your solution.
The assignment is in the files:
[Lexer.x][/src/Language/Nano/Lexer.x]
[Parser.y][/src/Language/Nano/Parser.y]
[Eval.hs][/src/Language/Nano/Lexer.x]
and
tests/Test.hs has some sample tests, and testing code that you will use to check your assignments before submitting.
You should only need to modify the parts of the files which say:
error "TBD: …"
with suitable Haskell implementations.
Note: Start early! Lexing and Parsing are new tools, which may take a while to grok.