Goals

I am going to show you how to make a DSL compiler in a single
sitting. It will be capable of:

consuming the DSL's concrete syntax
lexing and parsing
(you should already know how to do this)

constructing a semantic model
with all the bells and whistles
variables, functions, etc.
types and type inference
and strong safety properties
static compile-time checks
error messages with input coordinates			

emitting native code
which might actually be fast