To use lalrpop we'll need to add it to our dependencies and set up the build script. While we're at it, lets also make sure we've added inkwell and failure as dependencies (for LLVM bindings and error handling respectively).

First lets create a new cargo project. We'll structure it as a main calc crate with a small binary that just parses the command line arguments and sets everything up before calling into the central crate to run everything.

$ cargo new calc

Then update Cargo.toml:

# Cargo.toml

[package]
name = "calc"
version = "0.1.0"
authors = ["Michael Bryan <michaelfbryan@gmail.com>"]
build = "build.rs"

[dependencies]
inkwell = { git = "https://github.com/TheDan64/inkwell", features = ["llvm3-7"] }
failure = "0.1.1"
lalrpop-util = "0.14.0"
regex = "0.2.7"

[build-dependencies]
lalrpop = "0.14.0"

And the build script:

// build.rs

extern crate lalrpop;

fn main() {
    lalrpop::process_root().unwrap();
}

With the lalrpop build system set up we can lay out the crate's skeleton. It's usually a good idea to break each phase of a compiler (because that's what we're effectively making) out into their own modules, so here's the tentative directory structure:

• /
  • bin/
    • yalc.rs
  • src/
    • lib.rs
    • syntax/
      • mod.rs
      • ast.rs
      • grammar.lalrpop

At the moment, we've stubbed out the rust files with a bunch of extern crate and mod statements.