yes-lang

Yet anothEr Scripting Language

Simple interpreter in Rust: - "manual" tokenization - single-/multi-line comments - prefix & infix operators - Pratt parser impl - tree-walking interpreter - immutable scope-based bindings - functions as a first class citizens - lexer, parser, interpreter & REPL in <2k LoC

Goals: - learn by doing - easy to understand - easy to implement - easy to follow - test coverage

Non-goals: - IO - stdlib - safety - collections - performance - type-safety - production-readiness - usability in general

REPL

```shell $ cargo run [...] REPL: enter :q to quit.

let hi = fn(name) { "hello " + name }; [AST] hi("world") [AST] hello world :q $ ```

Run

```rust // examples/fib.yes

fn fib1(n, a, b) { if n == 0 { a+b } else { fib1(n-1, a+b, a) } }

fn fib(n) { if n <= 0 { 0 } else { if n <= 2 { 1 } else { fib1(n-2, 1, 0) } } }

fib(42) == 267914296 && fib(84) == 160500643816367088

```

shell $ cargo run examples/fib.yes [...] true