rust: add conj, stepA. Self-hosting!

11 files changed, 530 insertions, 13 deletions

diff --git a/rust/src/core.rs b/rust/src/core.rs
index c1abaf6..e751f88 100644
--- a/rust/src/core.rs
+++ b/rust/src/core.rs
@@ -7,7 +7,7 @@ use std::io::File;
 use types::{MalVal,MalRet,err_val,err_str,err_string,
             Nil,Int,Strn,List,Vector,Hash_Map,Func,MalFunc,Atom,
             _nil,_true,_false,_int,string,
-            list,listm,vectorm,hash_mapm,func,funcm,malfuncd};
+            list,vector,listm,vectorm,hash_mapm,func,funcm,malfuncd};
 use types;
 use readline;
 use reader;
@@ -209,7 +209,7 @@ pub fn keys(a:Vec<MalVal>) -> MalRet {
         Nil => return Ok(_nil()),
         _ => return err_str("contains? on non-hash map"),
     };
-    if hm.len() == 0 { return Ok(_nil()); }
+    //if hm.len() == 0 { return Ok(_nil()); }
     let mut keys = vec![];
     for k in hm.keys() {
         keys.push(string(k.to_string()));
@@ -227,7 +227,7 @@ pub fn vals(a:Vec<MalVal>) -> MalRet {
         Nil => return Ok(_nil()),
         _ => return err_str("contains? on non-hash map"),
     };
-    if hm.len() == 0 { return Ok(_nil()); }
+    //if hm.len() == 0 { return Ok(_nil()); }
     let mut vals = vec![];
     for k in hm.values() {
         vals.push(k.clone());
@@ -382,6 +382,30 @@ pub fn map(a:Vec<MalVal>) -> MalRet {
     Ok(list(results))
 }
 
+pub fn conj(a:Vec<MalVal>) -> MalRet {
+    if a.len() < 2 {
+        return err_str("Wrong arity to conj call");
+    }
+    let mut new_v:Vec<MalVal> = vec![];
+    match *a[0].clone() {
+        List(ref l,_) => {
+            new_v.push_all(l.as_slice());
+            for mv in a.iter().skip(1) {
+                new_v.insert(0,mv.clone());
+            }
+            Ok(list(new_v))
+        },
+        Vector(ref l,_) => {
+            new_v.push_all(l.as_slice());
+            for mv in a.iter().skip(1) {
+                new_v.push(mv.clone());
+            }
+            Ok(vector(new_v))
+        },
+        _ => return err_str("conj called with non-sequence"),
+    }
+}
+
 
 // Metadata functions
 fn with_meta(a:Vec<MalVal>) -> MalRet {
@@ -519,10 +543,12 @@ pub fn ns() -> HashMap<String,MalVal> {
     ns.insert("count".to_string(), func(count));
     ns.insert("apply".to_string(), func(apply));
     ns.insert("map".to_string(), func(map));
+    ns.insert("conj".to_string(), func(conj));
 
     ns.insert("with-meta".to_string(), func(with_meta));
     ns.insert("meta".to_string(), func(meta));
     ns.insert("atom".to_string(), func(types::atom));
+    ns.insert("atom?".to_string(), func(types::atom_q));
     ns.insert("deref".to_string(), func(deref));
     ns.insert("reset!".to_string(), func(reset_bang));
     ns.insert("swap!".to_string(), func(swap_bang));
diff --git a/rust/src/step2_eval.rs b/rust/src/step2_eval.rs
index 9e33042..2cf7897 100644
--- a/rust/src/step2_eval.rs
+++ b/rust/src/step2_eval.rs
@@ -38,7 +38,7 @@ fn eval_ast(ast: MalVal, env: &HashMap<String,MalVal>) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
diff --git a/rust/src/step3_env.rs b/rust/src/step3_env.rs
index 820f21d..cb80947 100644
--- a/rust/src/step3_env.rs
+++ b/rust/src/step3_env.rs
@@ -39,7 +39,7 @@ fn eval_ast(ast: MalVal, env: Env) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
diff --git a/rust/src/step4_if_fn_do.rs b/rust/src/step4_if_fn_do.rs
index 7fc8b51..1a8d271 100644
--- a/rust/src/step4_if_fn_do.rs
+++ b/rust/src/step4_if_fn_do.rs
@@ -40,7 +40,7 @@ fn eval_ast(ast: MalVal, env: Env) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
diff --git a/rust/src/step5_tco.rs b/rust/src/step5_tco.rs
index 0a51cdd..0fdc597 100644
--- a/rust/src/step5_tco.rs
+++ b/rust/src/step5_tco.rs
@@ -40,7 +40,7 @@ fn eval_ast(ast: MalVal, env: Env) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
diff --git a/rust/src/step6_file.rs b/rust/src/step6_file.rs
index 3503653..e1198bb 100644
--- a/rust/src/step6_file.rs
+++ b/rust/src/step6_file.rs
@@ -41,7 +41,7 @@ fn eval_ast(ast: MalVal, env: Env) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
diff --git a/rust/src/step7_quote.rs b/rust/src/step7_quote.rs
index acd487c..bdfdf24 100644
--- a/rust/src/step7_quote.rs
+++ b/rust/src/step7_quote.rs
@@ -92,7 +92,7 @@ fn eval_ast(ast: MalVal, env: Env) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
diff --git a/rust/src/step8_macros.rs b/rust/src/step8_macros.rs
index a4a1f75..3e5f8a7 100644
--- a/rust/src/step8_macros.rs
+++ b/rust/src/step8_macros.rs
@@ -151,7 +151,7 @@ fn eval_ast(ast: MalVal, env: Env) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
@@ -409,6 +409,8 @@ fn main() {
     // core.mal: defined using the language itself
     let _ = rep("(def! not (fn* (a) (if a false true)))", repl_env.clone());
     let _ = rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))", repl_env.clone());
+    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.clone());
+    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.clone());
 
     // Invoked with command line arguments
     let args = os::args();
diff --git a/rust/src/step9_try.rs b/rust/src/step9_try.rs
index 6e3cf29..c36abcb 100644
--- a/rust/src/step9_try.rs
+++ b/rust/src/step9_try.rs
@@ -151,7 +151,7 @@ fn eval_ast(ast: MalVal, env: Env) -> MalRet {
                 }
             }
             Ok(match *ast { List(_,_) => list(ast_vec),
-                            _       => vector(ast_vec) })
+                            _         => vector(ast_vec) })
         },
         Hash_Map(ref hm,_) => {
             let mut new_hm: HashMap<String,MalVal> = HashMap::new();
@@ -440,6 +440,8 @@ fn main() {
     let _ = rep("(def! *host-language* \"rust\")", repl_env.clone());
     let _ = rep("(def! not (fn* (a) (if a false true)))", repl_env.clone());
     let _ = rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))", repl_env.clone());
+    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.clone());
+    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.clone());
 
     // Invoked with command line arguments
     let args = os::args();
diff --git a/rust/src/stepA_interop.rs b/rust/src/stepA_interop.rs
new file mode 100644
index 0000000..c36abcb
--- /dev/null
+++ b/rust/src/stepA_interop.rs
@@ -0,0 +1,478 @@
+// support precompiled regexes in reader.rs
+#![feature(phase)]
+#[phase(plugin)]
+extern crate regex_macros;
+extern crate regex;
+
+use std::collections::HashMap;
+use std::os;
+
+use types::{MalVal,MalRet,MalError,ErrString,ErrMalVal,err_str,
+            Nil,False,Sym,List,Vector,Hash_Map,Func,MalFunc,
+            _nil,symbol,string,list,vector,hash_map,malfunc,malfuncd};
+use env::{Env,env_new,env_bind,env_root,env_find,env_set,env_get};
+mod readline;
+mod types;
+mod reader;
+mod printer;
+mod env;
+mod core;
+
+// read
+fn read(str: String) -> MalRet {
+    reader::read_str(str)
+}
+
+// eval
+fn is_pair(x: MalVal) -> bool {
+    match *x {
+        List(ref lst,_) => lst.len() > 0,
+        _ => false,
+    }
+}
+
+fn quasiquote(ast: MalVal) -> MalVal {
+    if !is_pair(ast.clone()) {
+        return list(vec![symbol("quote"), ast])
+    }
+
+    match *ast.clone() {
+        List(ref args,_) => {
+            let ref a0 = args[0];
+            match **a0 {
+                Sym(ref s) => {
+                    if s.to_string() == "unquote".to_string() {
+                        let ref a1 = args[1];
+                        return a1.clone();
+                    }
+                },
+                _ => (),
+            }
+            if is_pair(a0.clone()) {
+                match **a0 {
+                    List(ref a0args,_) => {
+                        let a00 = a0args[0].clone();
+                        match *a00 {
+                            Sym(ref s) => {
+                                if s.to_string() == "splice-unquote".to_string() {
+                                    return list(vec![symbol("concat"),
+                                                     a0args[1].clone(),
+                                                     quasiquote(list(args.slice(1,args.len()).to_vec()))])
+                                }
+                            },
+                            _ => (),
+                        }
+                    },
+                    _ => (),
+                }
+            }
+            let rest = list(args.slice(1,args.len()).to_vec());
+            return list(vec![symbol("cons"),
+                             quasiquote(a0.clone()),
+                             quasiquote(rest)])
+        },
+        _ => _nil(), // should never reach
+    }
+}
+
+fn is_macro_call(ast: MalVal, env: Env) -> bool {
+    match *ast {
+        List(ref lst,_) => {
+            let ref a0 = *lst[0];
+            match *a0 {
+                Sym(ref a0sym) => {
+                    if env_find(env.clone(), a0sym.to_string()).is_some() {
+                        match env_get(env, a0sym.to_string()) {
+                            Ok(f) => {
+                                match *f {
+                                    MalFunc(ref mfd,_) => {
+                                        mfd.is_macro
+                                    },
+                                    _ => false,
+                                }
+                            },
+                            _ => false,
+                        }
+                    } else {
+                        false
+                    }
+                },
+                _ => false,
+            }
+        },
+        _ => false,
+    }
+}
+
+fn macroexpand(mut ast: MalVal, env: Env) -> MalRet {
+    while is_macro_call(ast.clone(), env.clone()) {
+        let ast2 = ast.clone();
+        let args = match *ast2 {
+            List(ref args,_) => args,
+            _ => break,
+        };
+        let ref a0 = args[0];
+        let mf = match **a0 {
+            Sym(ref s) => {
+                match env_get(env.clone(), s.to_string()) {
+                    Ok(mf) => mf,
+                    Err(e) => return Err(e),
+                }
+            },
+            _ => break,
+        };
+        match *mf {
+            MalFunc(_,_) => {
+                match mf.apply(args.slice(1,args.len()).to_vec()) {
+                    Ok(r) => ast = r,
+                    Err(e) => return Err(e),
+                }
+            },
+            _ => break,
+        }
+    }
+    Ok(ast)
+}
+
+fn eval_ast(ast: MalVal, env: Env) -> MalRet {
+    let ast2 = ast.clone();
+    match *ast2 {
+    //match *ast {
+        Sym(ref sym) => {
+            env_get(env.clone(), sym.clone())
+        },
+        List(ref a,_) | Vector(ref a,_) => {
+            let mut ast_vec : Vec<MalVal> = vec![];
+            for mv in a.iter() {
+                let mv2 = mv.clone();
+                match eval(mv2, env.clone()) {
+                    Ok(mv) => { ast_vec.push(mv); },
+                    Err(e) => { return Err(e); },
+                }
+            }
+            Ok(match *ast { List(_,_) => list(ast_vec),
+                            _         => vector(ast_vec) })
+        },
+        Hash_Map(ref hm,_) => {
+            let mut new_hm: HashMap<String,MalVal> = HashMap::new();
+            for (key, value) in hm.iter() {
+                match eval(value.clone(), env.clone()) {
+                    Ok(mv) => { new_hm.insert(key.to_string(), mv); },
+                    Err(e) => return Err(e),
+                }
+            }
+            Ok(hash_map(new_hm))
+        },
+        _ => {
+            Ok(ast)
+        }
+    }
+}
+
+fn eval(mut ast: MalVal, mut env: Env) -> MalRet {
+    'tco: loop {
+
+    //println!("eval: {}, {}", ast, env.borrow());
+    //println!("eval: {}", ast);
+    let mut ast2 = ast.clone();
+    match *ast2 {
+        List(_,_) => (),  // continue
+        _ => return eval_ast(ast2, env),
+    }
+
+    // apply list
+    match macroexpand(ast2, env.clone()) {
+        Ok(a) => {
+            ast2 = a;
+        },
+        Err(e) => return Err(e),
+    }
+    match *ast2 {
+        List(_,_) => (),  // continue
+        _ => return Ok(ast2),
+    }
+    let ast3 = ast2.clone();
+
+    let (args, a0sym) = match *ast2 {
+        List(ref args,_) => {
+            if args.len() == 0 { 
+                return Ok(ast3);
+            }
+            let ref a0 = *args[0];
+            match *a0 {
+                Sym(ref a0sym) => (args, a0sym.as_slice()),
+                _ => (args, "__<fn*>__"),
+            }
+        },
+        _ => return err_str("Expected list"),
+    };
+
+    match a0sym {
+        "def!" => {
+            let a1 = (*args)[1].clone();
+            let a2 = (*args)[2].clone();
+            let res = eval(a2, env.clone());
+            match res {
+                Ok(r) => {
+                    match *a1 {
+                        Sym(ref s) => {
+                            env_set(&env.clone(), s.clone(), r.clone());
+                            return Ok(r);
+                        },
+                        _ => {
+                            return err_str("def! of non-symbol")
+                        }
+                    }
+                },
+                Err(e) => return Err(e),
+            }
+        },
+        "let*" => {
+            let let_env = env_new(Some(env.clone()));
+            let a1 = (*args)[1].clone();
+            let a2 = (*args)[2].clone();
+            match *a1 {
+                List(ref binds,_) | Vector(ref binds,_) => {
+                    let mut it = binds.iter();
+                    while it.len() >= 2 {
+                        let b = it.next().unwrap();
+                        let exp = it.next().unwrap();
+                        match **b {
+                            Sym(ref bstr) => {
+                                match eval(exp.clone(), let_env.clone()) {
+                                    Ok(r) => {
+                                        env_set(&let_env, bstr.clone(), r);
+                                    },
+                                    Err(e) => {
+                                        return Err(e);
+                                    },
+                                }
+                            },
+                            _ => {
+                                return err_str("let* with non-symbol binding");
+                            },
+                        }
+                    }
+                },
+                _ => return err_str("let* with non-list bindings"),
+            }
+            ast = a2;
+            env = let_env.clone();
+            continue 'tco;
+        },
+        "quote" => {
+            return Ok((*args)[1].clone());
+        },
+        "quasiquote" => {
+            let a1 = (*args)[1].clone();
+            ast = quasiquote(a1);
+            continue 'tco;
+        },
+        "defmacro!" => {
+            let a1 = (*args)[1].clone();
+            let a2 = (*args)[2].clone();
+            match eval(a2, env.clone()) {
+                Ok(r) => {
+                    match *r {
+                        MalFunc(ref mfd,_) => {
+                            match *a1 {
+                                Sym(ref s) => {
+                                    let mut new_mfd = mfd.clone();
+                                    new_mfd.is_macro = true;
+                                    let mf = malfuncd(new_mfd,_nil());
+                                    env_set(&env.clone(), s.clone(), mf.clone());
+                                    return Ok(mf);
+                                },
+                                _ => return err_str("def! of non-symbol"),
+                            }
+                        },
+                        _ => return err_str("def! of non-symbol"),
+                    }
+                },
+                Err(e) => return Err(e),
+            }
+        },
+        "macroexpand" => {
+            let a1 = (*args)[1].clone();
+            return macroexpand(a1, env.clone())
+        },
+        "try*" => {
+            let a1 = (*args)[1].clone();
+            match eval(a1, env.clone()) {
+                Ok(res) => return Ok(res),
+                Err(err) => {
+                    if args.len() < 3 { return Err(err); }
+                    let a2 = (*args)[2].clone();
+                    let cat = match *a2 {
+                        List(ref cat,_) => cat,
+                        _ => return err_str("invalid catch* clause"),
+                    };
+                    if cat.len() != 3 {
+                        return err_str("wrong arity to catch* clause");
+                    }
+                    let c1 = (*cat)[1].clone();
+                    let bstr = match *c1 {
+                        Sym(ref s) => s,
+                        _ => return err_str("invalid catch* binding"),
+                    };
+                    let exc = match err {
+                        ErrMalVal(mv) => mv,
+                        ErrString(s) => string(s),
+                    };
+                    let bind_env = env_new(Some(env.clone()));
+                    env_set(&bind_env, bstr.to_string(), exc);
+                    let c2 = (*cat)[2].clone();
+                    return eval(c2, bind_env);
+                },
+            };
+        }
+        "do" => {
+            let el = list(args.slice(1,args.len()-1).to_vec());
+            match eval_ast(el, env.clone()) {
+                Err(e) => return Err(e),
+                Ok(_) => {
+                    let ref last = args[args.len()-1];
+                    ast = last.clone();
+                    continue 'tco;
+                },
+            }
+        },
+        "if" => {
+            let a1 = (*args)[1].clone();
+            let cond = eval(a1, env.clone());
+            match cond {
+                Err(e) => return Err(e),
+                Ok(c) => match *c {
+                    False | Nil => {
+                        if args.len() >= 4 {
+                            let a3 = (*args)[3].clone();
+                            ast = a3;
+                            env = env.clone();
+                            continue 'tco;
+                        } else {
+                            return Ok(_nil());
+                        }
+                    },
+                    _ => {
+                        let a2 = (*args)[2].clone();
+                        ast = a2;
+                        env = env.clone();
+                        continue 'tco;
+                    },
+                }
+            }
+        },
+        "fn*" => {
+            let a1 = (*args)[1].clone();
+            let a2 = (*args)[2].clone();
+            return Ok(malfunc(eval, a2, env.clone(), a1, _nil()));
+        },
+        "eval" => {
+            let a1 = (*args)[1].clone();
+            match eval(a1, env.clone()) {
+                Ok(exp) => {
+                    ast = exp;
+                    env = env_root(&env);
+                    continue 'tco;
+                },
+                Err(e) => return Err(e),
+            }
+        },
+        _ => { // function call
+            return match eval_ast(ast3, env.clone()) {
+                Err(e) => Err(e),
+                Ok(el) => {
+                    let args = match *el {
+                        List(ref args,_) => args,
+                        _ => return err_str("Invalid apply"),
+                    };
+                    match *args.clone()[0] {
+                        Func(f,_) => f(args.slice(1,args.len()).to_vec()),
+                        MalFunc(ref mf,_) => {
+                            let mfc = mf.clone();
+                            let alst = list(args.slice(1,args.len()).to_vec());
+                            let new_env = env_new(Some(mfc.env.clone()));
+                            match env_bind(&new_env, mfc.params, alst) {
+                                Ok(_) => {
+                                    ast = mfc.exp;
+                                    env = new_env;
+                                    continue 'tco;
+                                },
+                                Err(e) => err_str(e.as_slice()),
+                            }
+                        },
+                        _ => err_str("attempt to call non-function"),
+                    }
+                }
+            }
+        },
+    }
+
+    }
+}
+
+// print
+fn print(exp: MalVal) -> String {
+    exp.pr_str(true)
+}
+
+fn rep(str: &str, env: Env) -> Result<String,MalError> {
+    match read(str.to_string()) {
+        Err(e) => Err(e),
+        Ok(ast) => {
+            //println!("read: {}", ast);
+            match eval(ast, env) {
+                Err(e)  => Err(e),
+                Ok(exp) => Ok(print(exp)),
+            }
+        }
+    }
+}
+
+fn main() {
+    // core.rs: defined using rust
+    let repl_env = env_new(None);
+    for (k, v) in core::ns().into_iter() { env_set(&repl_env, k, v); }
+    // see eval() for definition of "eval"
+    env_set(&repl_env, "*ARGV*".to_string(), list(vec![]));
+
+    // core.mal: defined using the language itself
+    let _ = rep("(def! *host-language* \"rust\")", repl_env.clone());
+    let _ = rep("(def! not (fn* (a) (if a false true)))", repl_env.clone());
+    let _ = rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))", repl_env.clone());
+    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.clone());
+    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.clone());
+
+    // Invoked with command line arguments
+    let args = os::args();
+    if args.len() > 1 {
+        let mv_args = args.slice(2,args.len()).iter()
+            .map(|a| string(a.to_string()))
+            .collect::<Vec<MalVal>>();
+        env_set(&repl_env, "*ARGV*".to_string(), list(mv_args));
+        let lf = "(load-file \"".to_string() + args[1] + "\")".to_string();
+        match rep(lf.as_slice(), repl_env.clone()) {
+            Ok(_) => {
+                os::set_exit_status(0);
+                return;
+            },
+            Err(str) => {
+                println!("Error: {}", str);
+                os::set_exit_status(1);
+                return;
+            },
+        }
+    }
+
+    // repl loop
+    let _  = rep("(println (str \"Mal [\" *host-language* \"]\"))", repl_env.clone());
+    loop {
+        let line = readline::mal_readline("user> ");
+        match line { None => break, _ => () }
+        match rep(line.unwrap().as_slice(), repl_env.clone()) {
+            Ok(str)  => println!("{}", str),
+            Err(ErrMalVal(_)) => (),  // Blank line
+            Err(ErrString(s)) => println!("Error: {}", s),
+        }
+    }
+}
diff --git a/rust/src/types.rs b/rust/src/types.rs
index e7e60f9..0b59716 100644
--- a/rust/src/types.rs
+++ b/rust/src/types.rs
@@ -247,7 +247,7 @@ pub fn vector_q(a:Vec<MalVal>) -> MalRet {
     }
     match *a[0].clone() {
         Vector(_,_) => Ok(_true()),
-        _         => Ok(_false()),
+        _           => Ok(_false()),
     }
 }
 
@@ -330,6 +330,15 @@ pub fn malfuncd(mfd: MalFuncData, meta: MalVal) -> MalVal {
 
 
 // Atoms
+pub fn atom_q(a:Vec<MalVal>) -> MalRet {
+    if a.len() != 1 {
+        return err_str("Wrong arity to atom? call");
+    }
+    match *a[0].clone() {
+        Atom(_) => Ok(_true()),
+        _       => Ok(_false()),
+    }
+}
 pub fn atom(a:Vec<MalVal>) -> MalRet {
     if a.len() != 1 {
         return err_str("Wrong arity to atom call");
@@ -345,6 +354,6 @@ pub fn sequential_q(a:Vec<MalVal>) -> MalRet {
     }
     match *a[0].clone() {
         List(_,_) | Vector(_,_) => Ok(_true()),
-        _                   => Ok(_false()),
+        _                       => Ok(_false()),
     }
 }