External DSLs

Getting the code

Follow the assignment workflow: fork to GitHub, then clone to your machine.

Alternatively, you can download the code and work locally.

Working on the lab

Extend the code to implement the following grammar:

        n ∈ 𝒵 
e ∈ Expr ::= e + t | e - t | t
t ∈ Term ::= t * f | t / f | f
f ∈ Fact ::= n | ( e )

It's best to add features in the following order:

1. subtraction
2. multiplication
3. division
4. parenthetical expressions

When you add a new feature to a language, extend the implemention in the following order:

1. Intermediate representation
   1. Data structures
   2. Sugar (if you want)
2. Parser
   1. Tests
   2. Implementation
3. Semantics
   1. Tests
   2. Implementation

Bonus

If you finish (or just want to explore things more), here are some options.

Better error-checking

Can you give better error-checking and error messages for the parser? For the read-eval-print loop? You could also write one or more semantic checks: a pass over the AST to check for errors, e.g., divide by literal 0.

More features

You could add more features to the language, including

• comparisons, e.g., <, >, =, etc.
• constants, e.g., built-in names such as π or e