mal/rust/step8_macros.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]
mod types;
use types::{MalVal,MalArgs,MalRet,MalErr,error,format_error};
use types::MalVal::{Nil,Bool,Str,Sym,List,Vector,Hash,Func,MalFunc};
mod reader;
mod printer;
mod env;
use env::{Env,env_new,env_bind,env_find,env_get,env_set,env_sets};
#[macro_use]
mod core;

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

// eval
fn quasiquote(ast: &MalVal) -> MalVal {
  match ast {
    List(ref v,_) | Vector(ref v,_) if v.len() > 0 => {
      let a0 = &v[0];
      match a0 {
        Sym(ref s) if s == "unquote" => v[1].clone(),
        _ => {
          match a0 {
            List(ref v0,_) | Vector(ref v0,_) if v0.len() > 0 => {
              match v0[0] {
                Sym(ref s) if s == "splice-unquote" => {
                  list![Sym("concat".to_string()),
                        v0[1].clone(),
                        quasiquote(&list!(v[1..].to_vec()))]
                },
                _ => {
                  list![Sym("cons".to_string()),
                        quasiquote(a0),
                        quasiquote(&list!(v[1..].to_vec()))]
                },
              }
            },
            _ => {
              list![Sym("cons".to_string()),
                    quasiquote(a0),
                    quasiquote(&list!(v[1..].to_vec()))]
            }
          }
        }
      }
    },
    _ => list![Sym("quote".to_string()), ast.clone()]
  }
}

fn is_macro_call(ast: &MalVal, env: &Env) -> Option<(MalVal,MalArgs)> {
  match ast {
    List(v,_) => {
      match v[0] {
        Sym(ref s) => {
          match env_find(env, s) {
            Some(e) => {
              match env_get(&e, &v[0]) {
                Ok(f @ MalFunc{is_macro: true, ..}) => {
                  Some((f, v[1..].to_vec()))
                },
                _ => None,
              }
            },
            _ => None,
          }
        },
        _ => None,
      }
    },
    _ => None,
  }
}

fn macroexpand(mut ast: MalVal, env: &Env) -> (bool, MalRet) {
  let mut was_expanded = false;
  while let Some((mf, args)) = is_macro_call(&ast, env) {
    //println!("macroexpand 1: {:?}", ast);
    ast = match mf.apply(args) {
      Err(e) => return (false, Err(e)),
      Ok(a) => a,
    };
    //println!("macroexpand 2: {:?}", ast);
    was_expanded = true;
  }
  ((was_expanded, Ok(ast)))
}

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,_) => {
      match macroexpand(ast.clone(), &env) {
        (true, Ok(new_ast)) => {
          ast = new_ast;
          continue 'tco;
        }
        (_, Err(e)) => return Err(e),
        _ => (),
      }

      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 == "quote" => {
          Ok(l[1].clone())
        },
        Sym(ref a0sym) if a0sym == "quasiquote" => {
          ast = quasiquote(&l[1]);
          continue 'tco;
        },
        Sym(ref a0sym) if a0sym == "defmacro!" => {
          let (a1, a2) = (l[1].clone(), l[2].clone());
          let r = eval(a2, env.clone())?;
          match r {
            MalFunc{eval, ast, env, params, ..} => {
              Ok(env_set(&env, a1.clone(),
                 MalFunc{eval: eval, ast: ast.clone(), env: env.clone(),
                         params: params.clone(), is_macro: true,
                         meta: Rc::new(Nil)})?)
            },
              _ => error("set_macro on non-function"),
          }
        },
        Sym(ref a0sym) if a0sym == "macroexpand" => {
          match macroexpand(l[1].clone(), &env) {
            (_, Ok(new_ast)) => Ok(new_ast),
            (_, e) => return e,
          }
        },
        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)})
        },
        Sym(ref a0sym) if a0sym == "eval" => {
          ast = eval(l[1].clone(), env.clone())?;
          while let Some(ref e) = env.clone().outer {
            env = e.clone();
          }
          continue 'tco;
        },
        _ => {
          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() {
  let mut args = std::env::args();
  let arg1 = args.nth(1);

  // `()` 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.");
  }

  // core.rs: defined using rust
  let repl_env = env_new(None);
  for (k, v) in core::ns() {
    env_sets(&repl_env, k, v);
  }
  env_sets(&repl_env, "*ARGV*", list!(args.map(Str).collect()));

  // core.mal: defined using the language itself
  let _ = rep("(def! not (fn* (a) (if a false true)))", &repl_env);
  let _ = rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))", &repl_env);
  let _ = rep("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))", &repl_env);
  let _ = rep("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))", &repl_env);


  // Invoked with arguments
  if let Some(f) = arg1 {
    match rep(&format!("(load-file \"{}\")",f), &repl_env) {
      Ok(_)  => std::process::exit(0),
      Err(e) => {
        println!("Error: {}", format_error(e));
        std::process::exit(1);
      }
    }
  }

  // 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
      }
    }
  }
}

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