This is a fully-functioning python-like language written in Rust using the
Parsel crate for lexing and parsing. The grammar, described in src/ast.rs,
closely mimics the provided grammar for DWISPY, except that (as we discussed) it
uses curly braces instead of indent/dedent tokens, and it uses semicolons
instead of newlines. These changes are necessary to make this work with the
library.
Once parsed, the language is evaluated straightforwardly; that code is in
src/eval.rs. The type-checker is in src/check.rs.
Type-checker in src/check.rs outlines the type-chekcing rules as specified on jimfix website.
We have implemented a trait Check that every block implements such that we are now able to type-check a strongly-typed DWISPY program and emit type errors on that stage. This works in a similar way as before, but with this additional Check step added during the front-end step.
Some features of the language:
- Assignment, update statements (
+=and friends), lookups - Arithmetic operations, parenthesized operations, proper order of operations
- If/else, comparison operations, boolean operations
- While loops
- IO (print and input)
- Functions and function calls
The structure is pretty simple. Parsel autogenerates a parser from the
programmatic description of the AST; the parser outputs the AST as that
structured data. We recursively evaluate the AST via the Eval trait, which is
implemented by each AST member. The only real non-obvious piece of code is for
binary operations; we have a trait BinOp that each type of operation
implements which describes how to combine two Values into a new Value, and
then we implement the Eval trait generic over all binary operations. This
creates a clean separation between the associativity logic and the
computational logic.