whilepp

A Teeny Tiny Type checker and Interpreter for WHILE++ to get some practice with

1. Parser combinators chumsky
2. Error handling Result
3. Type checking
4. Error reporting ariadne
5. Property based testing proptest

Part 1: Parse

Fill in the parse_todo!() inside parse.rs to parse expressions the WHILE++ language.

1. First, complete the implementations of parse_rel_expr and parse_expr. When you are done cargo test relational should work.

2. Next, define and use sub-parsers like if_only and try_ to parse one-armed if statements and try statements. When you are done cargo test statement should pass.

When you are done with both parts, cargo test parse should pass.

Part 2: Evaluate

Next, fill in the todo!() inside eval.rs to evaluate WHILE++ programs.

1. First, fill in eval_op and eval_expr to evaluate expressions. When you are done, cargo test eval should pass

2. Next, fill in eval_stmt to evaluate statements. When you are done, cargo test run should pass.

Part 3: Check

Finally, you will implement a small static checker for WHILE++ programs.

1. First, implement check_expr which checks that an Expr is well-typed in a given Env. When you are done, cargo test check_expr should pass.

2. Next, implement check_stmt which checks that a Stmt is well-typed in a given Env. When you are done, cargo test soundness should pass.

Specifically, the soundness tests check that if a program type-checks, then it will not produce a runtime type error when evaluated (divide by zero is ok).

When you are done with all the parts, cargo test check should pass.

Grading

Each test is worth 5 points; so you can run cargo test and figure out your score.

You can run python3 grade.py to do the tabulation automatically.

Submission

You can submit your assignment by running make turnin