Toy Lisp interpreter in Rust
If you want to mess around with this, run cargo run --release --example=repl.
The syntax is pretty similar to other lisps, but one big difference is that there's no concept of macros yet.
Everything, even pieces of syntax like def(short for define) and let, are regular old functions.
Therefore, anything that shouldn't be evaluated while being passed as an argument has to be quoted.
For instance, here's how you define a variable:
(def 'var 2)You have to quote the symbol because def isn't a special syntax definition, it's just a regular old function.
Without quoting the symbol, rlisp would try to evaluate it and fail to resolve it (since it hasn't been defined yet, we're defining it now!).
It's kind of a pure way of doing things, it's very clear how things will be evaluated when your code runs (everything is a regular function, even core pieces of syntax like def and if),
Mainly though, I did it this way because it's easier and I'm lazy.
Here's a function definition (it squares a number):
(def {square x}
{* x x})