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use std::env;
use std::fs;
use std::io;
use std::io::Write;
use std::process;
mod bytecode;
mod scanner;
mod treewalk;
/// Trait for making the different interpreters callable in the same
/// way.
pub trait Lox {
type Value;
type Error: std::fmt::Display;
fn create() -> Self;
fn interpret(
&mut self,
source: String,
) -> Result<Self::Value, Vec<Self::Error>>;
}
fn main() {
let mut args = env::args();
if args.len() > 2 {
println!("Usage: rlox [script]");
process::exit(1);
}
match env::var("LOX_INTERPRETER").as_ref().map(String::as_str) {
Ok("treewalk") => {
pick::<treewalk::interpreter::Interpreter>(args.nth(1))
}
_ => pick::<bytecode::Interpreter>(args.nth(1)),
}
}
fn pick<I: Lox>(file_arg: Option<String>) {
if let Some(file) = file_arg {
run_file::<I>(&file);
} else {
run_prompt::<I>();
}
}
// Run Lox code from a file and print results to stdout
fn run_file<I: Lox>(file: &str) {
let contents =
fs::read_to_string(file).expect("failed to read the input file");
let mut lox = I::create();
run(&mut lox, contents);
}
// Evaluate Lox code interactively in a shitty REPL.
fn run_prompt<I: Lox>() {
let mut line = String::new();
let mut lox = I::create();
loop {
print!("> ");
io::stdout().flush().unwrap();
io::stdin()
.read_line(&mut line)
.expect("failed to read user input");
run(&mut lox, std::mem::take(&mut line));
line.clear();
}
}
fn run<I: Lox>(lox: &mut I, code: String) {
if let Err(errors) = lox.interpret(code) {
for error in errors {
eprintln!("{}", error);
}
}
}
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