DISABLE FDs (REMOVE ME).

[jackhill/mal.git] / rust / step5_tco.rs

use std::rc::Rc;
//use std::collections::HashMap;
use fnv::FnvHashMap;
use itertools::Itertools;

#[macro_use]
extern crate lazy_static;
extern crate fnv;
extern crate itertools;
extern crate regex;

extern crate rustyline;
use rustyline::error::ReadlineError;
use rustyline::Editor;

#[macro_use]
mod types;
use crate::types::MalVal::{Bool, Func, Hash, List, MalFunc, Nil, Sym, Vector};
use crate::types::{error, format_error, MalArgs, MalErr, MalRet, MalVal};
mod env;
mod printer;
mod reader;
use crate::env::{env_bind, env_get, env_new, env_set, env_sets, Env};
#[macro_use]
mod core;

// read
fn read(str: &str) -> MalRet {
    reader::read_str(str.to_string())
}

// eval
fn eval_ast(ast: &MalVal, env: &Env) -> MalRet {
    match ast {
        Sym(_) => Ok(env_get(&env, &ast)?),
        List(v, _) => {
            let mut lst: MalArgs = vec![];
            for a in v.iter() {
                lst.push(eval(a.clone(), env.clone())?)
            }
            Ok(list!(lst))
        }
        Vector(v, _) => {
            let mut lst: MalArgs = vec![];
            for a in v.iter() {
                lst.push(eval(a.clone(), env.clone())?)
            }
            Ok(vector!(lst))
        }
        Hash(hm, _) => {
            let mut new_hm: FnvHashMap<String, MalVal> = FnvHashMap::default();
            for (k, v) in hm.iter() {
                new_hm.insert(k.to_string(), eval(v.clone(), env.clone())?);
            }
            Ok(Hash(Rc::new(new_hm), Rc::new(Nil)))
        }
        _ => Ok(ast.clone()),
    }
}

fn eval(mut ast: MalVal, mut env: Env) -> MalRet {
    let ret: MalRet;

    'tco: loop {
        ret = match ast.clone() {
            List(l, _) => {
                if l.len() == 0 {
                    return Ok(ast);
                }
                let a0 = &l[0];
                match a0 {
                    Sym(ref a0sym) if a0sym == "def!" => {
                        env_set(&env, l[1].clone(), eval(l[2].clone(), env.clone())?)
                    }
                    Sym(ref a0sym) if a0sym == "let*" => {
                        env = env_new(Some(env.clone()));
                        let (a1, a2) = (l[1].clone(), l[2].clone());
                        match a1 {
                            List(ref binds, _) | Vector(ref binds, _) => {
                                for (b, e) in binds.iter().tuples() {
                                    match b {
                                        Sym(_) => {
                                            let _ = env_set(
                                                &env,
                                                b.clone(),
                                                eval(e.clone(), env.clone())?,
                                            );
                                        }
                                        _ => {
                                            return error("let* with non-Sym binding");
                                        }
                                    }
                                }
                            }
                            _ => {
                                return error("let* with non-List bindings");
                            }
                        };
                        ast = a2;
                        continue 'tco;
                    }
                    Sym(ref a0sym) if a0sym == "do" => {
                        match eval_ast(&list!(l[1..l.len() - 1].to_vec()), &env)? {
                            List(_, _) => {
                                ast = l.last().unwrap_or(&Nil).clone();
                                continue 'tco;
                            }
                            _ => error("invalid do form"),
                        }
                    }
                    Sym(ref a0sym) if a0sym == "if" => {
                        let cond = eval(l[1].clone(), env.clone())?;
                        match cond {
                            Bool(false) | Nil if l.len() >= 4 => {
                                ast = l[3].clone();
                                continue 'tco;
                            }
                            Bool(false) | Nil => Ok(Nil),
                            _ if l.len() >= 3 => {
                                ast = l[2].clone();
                                continue 'tco;
                            }
                            _ => Ok(Nil),
                        }
                    }
                    Sym(ref a0sym) if a0sym == "fn*" => {
                        let (a1, a2) = (l[1].clone(), l[2].clone());
                        Ok(MalFunc {
                            eval: eval,
                            ast: Rc::new(a2),
                            env: env,
                            params: Rc::new(a1),
                            is_macro: false,
                            meta: Rc::new(Nil),
                        })
                    }
                    _ => match eval_ast(&ast, &env)? {
                        List(ref el, _) => {
                            let ref f = el[0].clone();
                            let args = el[1..].to_vec();
                            match f {
                                Func(_, _) => f.apply(args),
                                MalFunc {
                                    ast: mast,
                                    env: menv,
                                    params,
                                    ..
                                } => {
                                    let a = &**mast;
                                    let p = &**params;
                                    env = env_bind(Some(menv.clone()), p.clone(), args)?;
                                    ast = a.clone();
                                    continue 'tco;
                                }
                                _ => error("attempt to call non-function"),
                            }
                        }
                        _ => error("expected a list"),
                    },
                }
            }
            _ => eval_ast(&ast, &env),
        };

        break;
    } // end 'tco loop

    ret
}

// print
fn print(ast: &MalVal) -> String {
    ast.pr_str(true)
}

fn rep(str: &str, env: &Env) -> Result<String, MalErr> {
    let ast = read(str)?;
    let exp = eval(ast, env.clone())?;
    Ok(print(&exp))
}

fn main() {
    // `()` can be used when no completer is required
    let mut rl = Editor::<()>::new();
    if rl.load_history(".mal-history").is_err() {
        eprintln!("No previous history.");
    }

    // core.rs: defined using rust
    let repl_env = env_new(None);
    for (k, v) in core::ns() {
        env_sets(&repl_env, k, v);
    }

    // core.mal: defined using the language itself
    let _ = rep("(def! not (fn* (a) (if a false true)))", &repl_env);

    // main repl loop
    loop {
        let readline = rl.readline("user> ");
        match readline {
            Ok(line) => {
                rl.add_history_entry(&line);
                rl.save_history(".mal-history").unwrap();
                if line.len() > 0 {
                    match rep(&line, &repl_env) {
                        Ok(out) => println!("{}", out),
                        Err(e) => println!("Error: {}", format_error(e)),
                    }
                }
            }
            Err(ReadlineError::Interrupted) => continue,
            Err(ReadlineError::Eof) => break,
            Err(err) => {
                println!("Error: {:?}", err);
                break;
            }
        }
    }
}