mal/rust/step3_env.rs

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

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

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

#[macro_use]
#[allow(dead_code)]
mod types;
use types::{MalVal,MalArgs,MalRet,MalErr,error,format_error,func};
use types::MalVal::{Nil,Int,Sym,List,Vector,Hash};
mod reader;
mod printer;
mod env;
use env::{Env,env_new,env_get,env_set,env_sets};

// 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(ast: MalVal, env: Env) -> MalRet {
  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*" => {
          let 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(&let_env, b.clone(),
                                    eval(e.clone(), let_env.clone())?);
                  },
                  _ => { 
                    return error("let* with non-Sym binding");
                  }
                }
              }
            },
            _ => {
              return error("let* with non-List bindings");
            }
          };
          eval(a2, let_env)
        },
        _ => {
          match eval_ast(&ast, &env)? {
            List(ref el,_) => {
              let ref f = el[0].clone();
              f.apply(el[1..].to_vec())
            },
            _ => {
              error("expected a list")
            }
          }
        }
      }
    },
    _ => eval_ast(&ast, &env),
  }
}

// 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 int_op(op: fn(i64, i64) -> i64, a:MalArgs) -> MalRet {
  match (a[0].clone(), a[1].clone()) {
    (Int(a0), Int(a1)) => Ok(Int(op(a0,a1))),
    _ => error("invalid int_op args"),
  }
}

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

  let repl_env = env_new(None);
  env_sets(&repl_env, "+", func(|a:MalArgs|{int_op(|i,j|{i+j},a)}));
  env_sets(&repl_env, "-", func(|a:MalArgs|{int_op(|i,j|{i-j},a)}));
  env_sets(&repl_env, "*", func(|a:MalArgs|{int_op(|i,j|{i*j},a)}));
  env_sets(&repl_env, "/", func(|a:MalArgs|{int_op(|i,j|{i/j},a)}));

  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
      }
    }
  }
}

// vim: ts=2:sw=2:expandtab