示例#1
0
 static MalVal eval_ast(MalVal ast, Env env)
 {
     if (ast is MalSymbol)
     {
         return(env.get((MalSymbol)ast));
     }
     else if (ast is MalList)
     {
         MalList old_lst = (MalList)ast;
         MalList new_lst = ast.list_Q() ? new MalList()
                                     : (MalList) new MalVector();
         foreach (MalVal mv in old_lst.getValue())
         {
             new_lst.conj_BANG(EVAL(mv, env));
         }
         return(new_lst);
     }
     else if (ast is MalHashMap)
     {
         var new_dict = new Dictionary <string, MalVal>();
         foreach (var entry in ((MalHashMap)ast).getValue())
         {
             new_dict.Add(entry.Key, EVAL((MalVal)entry.Value, env));
         }
         return(new MalHashMap(new_dict));
     }
     else
     {
         return(ast);
     }
 }
示例#2
0
 public MalFunc(MalVal ast, Mal.env.Env env, MalList fparams,
                Func <MalList, MalVal> fn)
 {
     this.fn      = fn;
     this.ast     = ast;
     this.env     = env;
     this.fparams = fparams;
 }
示例#3
0
 public static MalVal macroexpand(MalVal ast, Env env) {
     while (is_macro_call(ast, env)) {
         MalSymbol a0 = (MalSymbol)((MalList)ast)[0];
         MalFunc mac = (MalFunc) env.get(a0);
         ast = mac.apply(((MalList)ast).rest());
     }
     return ast;
 }
示例#4
0
 public static MalVal macroexpand(MalVal ast, Env env)
 {
     while (is_macro_call(ast, env))
     {
         MalSymbol a0  = (MalSymbol)((MalList)ast)[0];
         MalFunc   mac = (MalFunc)env.get(a0);
         ast = mac.apply(((MalList)ast).rest());
     }
     return(ast);
 }
示例#5
0
        static MalVal EVAL(MalVal orig_ast, Env env)
        {
            MalVal  a0, a1, a2, res;
            MalList el;

            //Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
            if (!orig_ast.list_Q())
            {
                return(eval_ast(orig_ast, env));
            }

            // apply list
            MalList ast = (MalList)orig_ast;

            if (ast.size() == 0)
            {
                return(ast);
            }
            a0 = ast[0];
            if (!(a0 is MalSymbol))
            {
                throw new Mal.types.MalError("attempt to apply on non-symbol '"
                                             + Mal.printer._pr_str(a0, true) + "'");
            }

            switch (((MalSymbol)a0).getName())
            {
            case "def!":
                a1  = ast[1];
                a2  = ast[2];
                res = EVAL(a2, env);
                env.set((MalSymbol)a1, res);
                return(res);

            case "let*":
                a1 = ast[1];
                a2 = ast[2];
                MalSymbol key;
                MalVal    val;
                Env       let_env = new Env(env);
                for (int i = 0; i < ((MalList)a1).size(); i += 2)
                {
                    key = (MalSymbol)((MalList)a1)[i];
                    val = ((MalList)a1)[i + 1];
                    let_env.set(key, EVAL(val, let_env));
                }
                return(EVAL(a2, let_env));

            default:
                el = (MalList)eval_ast(ast, env);
                var f = (MalFunc)el[0];
                return(f.apply(el.rest()));
            }
        }
示例#6
0
 public static bool is_macro_call(MalVal ast, Env env) {
     if (ast is MalList) {
         MalVal a0 = ((MalList)ast)[0];
         if (a0 is MalSymbol &&
             env.find((MalSymbol)a0) != null) {
             MalVal mac = env.get((MalSymbol)a0);
             if (mac is MalFunc &&
                 ((MalFunc)mac).isMacro()) {
                 return true;
             }
         }
     }
     return false;
 }
示例#7
0
 public static bool is_macro_call(MalVal ast, Env env)
 {
     if (ast is MalList)
     {
         MalVal a0 = ((MalList)ast)[0];
         if (a0 is MalSymbol &&
             env.find((MalSymbol)a0) != null)
         {
             MalVal mac = env.get((MalSymbol)a0);
             if (mac is MalFunc &&
                 ((MalFunc)mac).isMacro())
             {
                 return(true);
             }
         }
     }
     return(false);
 }
示例#8
0
        static MalVal EVAL(MalVal orig_ast, Env env) {
            MalVal a0, a1, a2, res;
            MalList el;
            //Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
            if (!orig_ast.list_Q()) {
                return eval_ast(orig_ast, env);
            }

            // apply list
            MalList ast = (MalList)orig_ast;
            if (ast.size() == 0) { return ast; }
            a0 = ast[0];
            if (!(a0 is MalSymbol)) {
                throw new Mal.types.MalError("attempt to apply on non-symbol '"
                        + Mal.printer._pr_str(a0,true) + "'");
            }

            switch (((MalSymbol)a0).getName()) {
            case "def!":
                a1 = ast[1];
                a2 = ast[2];
                res = EVAL(a2, env);
                env.set((MalSymbol)a1, res);
                return res;
            case "let*":
                a1 = ast[1];
                a2 = ast[2];
                MalSymbol key;
                MalVal val;
                Env let_env = new Env(env);
                for(int i=0; i<((MalList)a1).size(); i+=2) {
                    key = (MalSymbol)((MalList)a1)[i];
                    val = ((MalList)a1)[i+1];
                    let_env.set(key, EVAL(val, let_env));
                }
                return EVAL(a2, let_env);
            default:
                el = (MalList)eval_ast(ast, env);
                var f = (MalFunc)el[0];
                return f.apply(el.rest());
            }
        }
示例#9
0
 // eval
 static MalVal eval_ast(MalVal ast, Env env) {
     if (ast is MalSymbol) {
         return env.get((MalSymbol)ast);
     } else if (ast is MalList) {
         MalList old_lst = (MalList)ast;
         MalList new_lst = ast.list_Q() ? new MalList()
                                     : (MalList)new MalVector();
         foreach (MalVal mv in old_lst.getValue()) {
             new_lst.conj_BANG(EVAL(mv, env));
         }
         return new_lst;
     } else if (ast is MalHashMap) {
         var new_dict = new Dictionary<string, MalVal>();
         foreach (var entry in ((MalHashMap)ast).getValue()) {
             new_dict.Add(entry.Key, EVAL((MalVal)entry.Value, env));
         }
         return new MalHashMap(new_dict);
     } else {
         return ast;
     }
 }
示例#10
0
文件: step6_file.cs 项目: nboyd/mal
        static MalVal EVAL(MalVal orig_ast, Env env)
        {
            MalVal a0, a1, a2, res;
            MalList el;

            while (true) {

            //Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
            if (!orig_ast.list_Q()) {
                return eval_ast(orig_ast, env);
            }

            // apply list
            MalList ast = (MalList)orig_ast;
            if (ast.size() == 0) { return ast; }
            a0 = ast[0];

            String a0sym = a0 is MalSymbol ? ((MalSymbol)a0).getName()
                                           : "__<*fn*>__";

            switch (a0sym) {
            case "def!":
                a1 = ast[1];
                a2 = ast[2];
                res = EVAL(a2, env);
                env.set((MalSymbol)a1, res);
                return res;
            case "let*":
                a1 = ast[1];
                a2 = ast[2];
                MalSymbol key;
                MalVal val;
                Env let_env = new Env(env);
                for(int i=0; i<((MalList)a1).size(); i+=2) {
                    key = (MalSymbol)((MalList)a1)[i];
                    val = ((MalList)a1)[i+1];
                    let_env.set(key, EVAL(val, let_env));
                }
                orig_ast = a2;
                env = let_env;
                break;
            case "do":
                eval_ast(ast.slice(1, ast.size()-1), env);
                orig_ast = ast[ast.size()-1];
                break;
            case "if":
                a1 = ast[1];
                MalVal cond = EVAL(a1, env);
                if (cond == Mal.types.Nil || cond == Mal.types.False) {
                    // eval false slot form
                    if (ast.size() > 3) {
                        orig_ast = ast[3];
                    } else {
                        return Mal.types.Nil;
                    }
                } else {
                    // eval true slot form
                    orig_ast = ast[2];
                }
                break;
            case "fn*":
                MalList a1f = (MalList)ast[1];
                MalVal a2f = ast[2];
                Env cur_env = env;
                return new MalFunc(a2f, env, a1f,
                    args => EVAL(a2f, new Env(cur_env, a1f, args)) );
            default:
                el = (MalList)eval_ast(ast, env);
                var f = (MalFunc)el[0];
                MalVal fnast = f.getAst();
                if (fnast != null) {
                    orig_ast = fnast;
                    env = f.genEnv(el.rest());
                } else {
                    return f.apply(el.rest());
                }
                break;
            }

            }
        }
示例#11
0
 public static MalVal RE(string str, Env env)
 {
     return(EVAL(READ(str), env));
 }
示例#12
0
        static MalVal EVAL(MalVal orig_ast, Env env)
        {
            MalVal  a0, a1, a2, res;
            MalList el;

            while (true)
            {
                //Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
                if (!orig_ast.list_Q())
                {
                    return(eval_ast(orig_ast, env));
                }

                // apply list
                MalVal expanded = macroexpand(orig_ast, env);
                if (!expanded.list_Q())
                {
                    return(eval_ast(expanded, env));
                }
                MalList ast = (MalList)expanded;

                if (ast.size() == 0)
                {
                    return(ast);
                }
                a0 = ast[0];

                String a0sym = a0 is MalSymbol ? ((MalSymbol)a0).getName()
                                           : "__<*fn*>__";

                switch (a0sym)
                {
                case "def!":
                    a1  = ast[1];
                    a2  = ast[2];
                    res = EVAL(a2, env);
                    env.set((MalSymbol)a1, res);
                    return(res);

                case "let*":
                    a1 = ast[1];
                    a2 = ast[2];
                    MalSymbol key;
                    MalVal    val;
                    Env       let_env = new Env(env);
                    for (int i = 0; i < ((MalList)a1).size(); i += 2)
                    {
                        key = (MalSymbol)((MalList)a1)[i];
                        val = ((MalList)a1)[i + 1];
                        let_env.set(key, EVAL(val, let_env));
                    }
                    orig_ast = a2;
                    env      = let_env;
                    break;

                case "quote":
                    return(ast[1]);

                case "quasiquote":
                    orig_ast = quasiquote(ast[1]);
                    break;

                case "defmacro!":
                    a1  = ast[1];
                    a2  = ast[2];
                    res = EVAL(a2, env);
                    ((MalFunc)res).setMacro();
                    env.set(((MalSymbol)a1), res);
                    return(res);

                case "macroexpand":
                    a1 = ast[1];
                    return(macroexpand(a1, env));

                case "try*":
                    try {
                        return(EVAL(ast[1], env));
                    } catch (Exception e) {
                        if (ast.size() > 2)
                        {
                            MalVal exc;
                            a2 = ast[2];
                            MalVal a20 = ((MalList)a2)[0];
                            if (((MalSymbol)a20).getName() == "catch*")
                            {
                                if (e is Mal.types.MalException)
                                {
                                    exc = ((Mal.types.MalException)e).getValue();
                                }
                                else
                                {
                                    exc = new MalString(e.Message);
                                }
                                return(EVAL(((MalList)a2)[2],
                                            new Env(env, ((MalList)a2).slice(1, 2),
                                                    new MalList(exc))));
                            }
                        }
                        throw e;
                    }

                case "do":
                    eval_ast(ast.slice(1, ast.size() - 1), env);
                    orig_ast = ast[ast.size() - 1];
                    break;

                case "if":
                    a1 = ast[1];
                    MalVal cond = EVAL(a1, env);
                    if (cond == Mal.types.Nil || cond == Mal.types.False)
                    {
                        // eval false slot form
                        if (ast.size() > 3)
                        {
                            orig_ast = ast[3];
                        }
                        else
                        {
                            return(Mal.types.Nil);
                        }
                    }
                    else
                    {
                        // eval true slot form
                        orig_ast = ast[2];
                    }
                    break;

                case "fn*":
                    MalList a1f     = (MalList)ast[1];
                    MalVal  a2f     = ast[2];
                    Env     cur_env = env;
                    return(new MalFunc(a2f, env, a1f,
                                       args => EVAL(a2f, new Env(cur_env, a1f, args))));

                default:
                    el = (MalList)eval_ast(ast, env);
                    var    f     = (MalFunc)el[0];
                    MalVal fnast = f.getAst();
                    if (fnast != null)
                    {
                        orig_ast = fnast;
                        env      = f.genEnv(el.rest());
                    }
                    else
                    {
                        return(f.apply(el.rest()));
                    }
                    break;
                }
            }
        }
示例#13
0
        // eval
        static MalVal EVAL(MalVal orig_ast, Env env)
        {
            MalVal a0, a1, a2, res;
            MalVal dbgeval = env.get("DEBUG-EVAL");

            if (dbgeval != null && dbgeval != Mal.types.Nil &&
                dbgeval != Mal.types.False)
            {
                Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
            }
            if (orig_ast is MalSymbol)
            {
                string key = ((MalSymbol)orig_ast).getName();
                res = env.get(key);
                if (res == null)
                {
                    throw new Mal.types.MalException("'" + key + "' not found");
                }
                return(res);
            }
            else if (orig_ast is MalVector)
            {
                MalVector old_lst = (MalVector)orig_ast;
                MalVector new_lst = new MalVector();
                foreach (MalVal mv in old_lst.getValue())
                {
                    new_lst.conj_BANG(EVAL(mv, env));
                }
                return(new_lst);
            }
            else if (orig_ast is MalHashMap)
            {
                var new_dict = new Dictionary <string, MalVal>();
                foreach (var entry in ((MalHashMap)orig_ast).getValue())
                {
                    new_dict.Add(entry.Key, EVAL((MalVal)entry.Value, env));
                }
                return(new MalHashMap(new_dict));
            }
            else if (!(orig_ast is MalList))
            {
                return(orig_ast);
            }

            // apply list
            MalList ast = (MalList)orig_ast;

            if (ast.size() == 0)
            {
                return(ast);
            }
            a0 = ast[0];
            if (!(a0 is MalSymbol))
            {
                throw new Mal.types.MalError("attempt to apply on non-symbol '"
                                             + Mal.printer._pr_str(a0, true) + "'");
            }

            switch (((MalSymbol)a0).getName())
            {
            case "def!":
                a1  = ast[1];
                a2  = ast[2];
                res = EVAL(a2, env);
                env.set((MalSymbol)a1, res);
                return(res);

            case "let*":
                a1 = ast[1];
                a2 = ast[2];
                MalSymbol key;
                MalVal    val;
                Env       let_env = new Env(env);
                for (int i = 0; i < ((MalList)a1).size(); i += 2)
                {
                    key = (MalSymbol)((MalList)a1)[i];
                    val = ((MalList)a1)[i + 1];
                    let_env.set(key, EVAL(val, let_env));
                }
                return(EVAL(a2, let_env));

            default:
                MalFunc f         = (MalFunc)EVAL(ast[0], env);
                MalList arguments = new MalList();
                foreach (MalVal mv in ast.rest().getValue())
                {
                    arguments.conj_BANG(EVAL(mv, env));
                }
                return(f.apply(arguments));
            }
        }
示例#14
0
        static MalVal EVAL(MalVal orig_ast, Env env)
        {
            MalVal  a0, a1, a2, res;
            MalList el;

            while (true)
            {
                //Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
                if (!orig_ast.list_Q())
                {
                    return(eval_ast(orig_ast, env));
                }

                // apply list
                MalList ast = (MalList)orig_ast;
                if (ast.size() == 0)
                {
                    return(ast);
                }
                a0 = ast[0];

                String a0sym = a0 is MalSymbol ? ((MalSymbol)a0).getName()
                                           : "__<*fn*>__";

                switch (a0sym)
                {
                case "def!":
                    a1  = ast[1];
                    a2  = ast[2];
                    res = EVAL(a2, env);
                    env.set((MalSymbol)a1, res);
                    return(res);

                case "let*":
                    a1 = ast[1];
                    a2 = ast[2];
                    MalSymbol key;
                    MalVal    val;
                    Env       let_env = new Env(env);
                    for (int i = 0; i < ((MalList)a1).size(); i += 2)
                    {
                        key = (MalSymbol)((MalList)a1)[i];
                        val = ((MalList)a1)[i + 1];
                        let_env.set(key, EVAL(val, let_env));
                    }
                    orig_ast = a2;
                    env      = let_env;
                    break;

                case "quote":
                    return(ast[1]);

                case "quasiquote":
                    orig_ast = quasiquote(ast[1]);
                    break;

                case "do":
                    eval_ast(ast.slice(1, ast.size() - 1), env);
                    orig_ast = ast[ast.size() - 1];
                    break;

                case "if":
                    a1 = ast[1];
                    MalVal cond = EVAL(a1, env);
                    if (cond == Mal.types.Nil || cond == Mal.types.False)
                    {
                        // eval false slot form
                        if (ast.size() > 3)
                        {
                            orig_ast = ast[3];
                        }
                        else
                        {
                            return(Mal.types.Nil);
                        }
                    }
                    else
                    {
                        // eval true slot form
                        orig_ast = ast[2];
                    }
                    break;

                case "fn*":
                    MalList a1f     = (MalList)ast[1];
                    MalVal  a2f     = ast[2];
                    Env     cur_env = env;
                    return(new MalFunc(a2f, env, a1f,
                                       args => EVAL(a2f, new Env(cur_env, a1f, args))));

                default:
                    el = (MalList)eval_ast(ast, env);
                    var    f     = (MalFunc)el[0];
                    MalVal fnast = f.getAst();
                    if (fnast != null)
                    {
                        orig_ast = fnast;
                        env      = f.genEnv(el.rest());
                    }
                    else
                    {
                        return(f.apply(el.rest()));
                    }
                    break;
                }
            }
        }
示例#15
0
文件: types.cs 项目: csellsword/mal
 public MalFunc(MalVal ast, Mal.env.Env env, MalList fparams,
                    Func<MalList, MalVal> fn) {
     this.fn = fn;
     this.ast = ast;
     this.env = env;
     this.fparams = fparams;
 }
示例#16
0
        static MalVal EVAL(MalVal orig_ast, Env env) {
            MalVal a0, a1, a2, res;
            MalList el;

            while (true) {

            //Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
            if (!orig_ast.list_Q()) {
                return eval_ast(orig_ast, env);
            }

            // apply list
            MalVal expanded = macroexpand(orig_ast, env);
            if (!expanded.list_Q()) {
                return eval_ast(expanded, env);
            } 
            MalList ast = (MalList) expanded;

            if (ast.size() == 0) { return ast; }
            a0 = ast[0];

            String a0sym = a0 is MalSymbol ? ((MalSymbol)a0).getName()
                                           : "__<*fn*>__";

            switch (a0sym) {
            case "def!":
                a1 = ast[1];
                a2 = ast[2];
                res = EVAL(a2, env);
                env.set((MalSymbol)a1, res);
                return res;
            case "let*":
                a1 = ast[1];
                a2 = ast[2];
                MalSymbol key;
                MalVal val;
                Env let_env = new Env(env);
                for(int i=0; i<((MalList)a1).size(); i+=2) {
                    key = (MalSymbol)((MalList)a1)[i];
                    val = ((MalList)a1)[i+1];
                    let_env.set(key, EVAL(val, let_env));
                }
                orig_ast = a2;
                env = let_env;
                break;
            case "quote":
                return ast[1];
            case "quasiquote":
                orig_ast = quasiquote(ast[1]);
                break;
            case "defmacro!":
                a1 = ast[1];
                a2 = ast[2];
                res = EVAL(a2, env);
                ((MalFunc)res).setMacro();
                env.set(((MalSymbol)a1), res);
                return res;
            case "macroexpand":
                a1 = ast[1];
                return macroexpand(a1, env);
            case "try*":
                try {
                    return EVAL(ast[1], env);
                } catch (Exception e) {
                    if (ast.size() > 2) {
                        MalVal exc;
                        a2 = ast[2];
                        MalVal a20 = ((MalList)a2)[0];
                        if (((MalSymbol)a20).getName() == "catch*") {
                            if (e is Mal.types.MalException) {
                                exc = ((Mal.types.MalException)e).getValue();
                            } else {
                                exc = new MalString(e.StackTrace);
                            }
                            return EVAL(((MalList)a2)[2],
                                        new Env(env, ((MalList)a2).slice(1,2),
                                                new MalList(exc)));
                        }
                    }
                    throw e;
                }
            case "do":
                eval_ast(ast.slice(1, ast.size()-1), env);
                orig_ast = ast[ast.size()-1];
                break;
            case "if":
                a1 = ast[1];
                MalVal cond = EVAL(a1, env);
                if (cond == Mal.types.Nil || cond == Mal.types.False) {
                    // eval false slot form
                    if (ast.size() > 3) {
                        orig_ast = ast[3];
                    } else {
                        return Mal.types.Nil;
                    }
                } else {
                    // eval true slot form
                    orig_ast = ast[2];
                }
                break;
            case "fn*":
                MalList a1f = (MalList)ast[1];
                MalVal a2f = ast[2];
                Env cur_env = env;
                return new MalFunc(a2f, env, a1f,
                    args => EVAL(a2f, new Env(cur_env, a1f, args)) );
            default:
                el = (MalList)eval_ast(ast, env);
                var f = (MalFunc)el[0];
                MalVal fnast = f.getAst();
                if (fnast != null) {
                    orig_ast = fnast;
                    env = f.genEnv(el.rest());
                } else {
                    return f.apply(el.rest());
                }
                break;
            }

            }
        }
示例#17
0
 public Interpreter(Env env)
 {
     this.env = env;
     Initialize();
 }
示例#18
0
        static MalVal EVAL(MalVal orig_ast, Env env)
        {
            MalVal a0, a1, a2, res;

            while (true)
            {
                MalVal dbgeval = env.get("DEBUG-EVAL");
                if (dbgeval != null && dbgeval != Mal.types.Nil &&
                    dbgeval != Mal.types.False)
                {
                    Console.WriteLine("EVAL: " + printer._pr_str(orig_ast, true));
                }
                if (orig_ast is MalSymbol)
                {
                    string key = ((MalSymbol)orig_ast).getName();
                    res = env.get(key);
                    if (res == null)
                    {
                        throw new Mal.types.MalException("'" + key + "' not found");
                    }
                    return(res);
                }
                else if (orig_ast is MalVector)
                {
                    MalVector old_lst = (MalVector)orig_ast;
                    MalVector new_lst = new MalVector();
                    foreach (MalVal mv in old_lst.getValue())
                    {
                        new_lst.conj_BANG(EVAL(mv, env));
                    }
                    return(new_lst);
                }
                else if (orig_ast is MalHashMap)
                {
                    var new_dict = new Dictionary <string, MalVal>();
                    foreach (var entry in ((MalHashMap)orig_ast).getValue())
                    {
                        new_dict.Add(entry.Key, EVAL((MalVal)entry.Value, env));
                    }
                    return(new MalHashMap(new_dict));
                }
                else if (!(orig_ast is MalList))
                {
                    return(orig_ast);
                }

                // apply list
                MalList ast = (MalList)orig_ast;

                if (ast.size() == 0)
                {
                    return(ast);
                }
                a0 = ast[0];

                String a0sym = a0 is MalSymbol ? ((MalSymbol)a0).getName()
                                           : "__<*fn*>__";

                switch (a0sym)
                {
                case "def!":
                    a1  = ast[1];
                    a2  = ast[2];
                    res = EVAL(a2, env);
                    env.set((MalSymbol)a1, res);
                    return(res);

                case "let*":
                    a1 = ast[1];
                    a2 = ast[2];
                    MalSymbol key;
                    MalVal    val;
                    Env       let_env = new Env(env);
                    for (int i = 0; i < ((MalList)a1).size(); i += 2)
                    {
                        key = (MalSymbol)((MalList)a1)[i];
                        val = ((MalList)a1)[i + 1];
                        let_env.set(key, EVAL(val, let_env));
                    }
                    orig_ast = a2;
                    env      = let_env;
                    break;

                case "quote":
                    return(ast[1]);

                case "quasiquote":
                    orig_ast = quasiquote(ast[1]);
                    break;

                case "do":
                    foreach (MalVal mv in ast.slice(1, ast.size() - 1).getValue())
                    {
                        EVAL(mv, env);
                    }
                    orig_ast = ast[ast.size() - 1];
                    break;

                case "if":
                    a1 = ast[1];
                    MalVal cond = EVAL(a1, env);
                    if (cond == Mal.types.Nil || cond == Mal.types.False)
                    {
                        // eval false slot form
                        if (ast.size() > 3)
                        {
                            orig_ast = ast[3];
                        }
                        else
                        {
                            return(Mal.types.Nil);
                        }
                    }
                    else
                    {
                        // eval true slot form
                        orig_ast = ast[2];
                    }
                    break;

                case "fn*":
                    MalList a1f     = (MalList)ast[1];
                    MalVal  a2f     = ast[2];
                    Env     cur_env = env;
                    return(new MalFunc(a2f, env, a1f,
                                       args => EVAL(a2f, new Env(cur_env, a1f, args))));

                default:
                    MalFunc f         = (MalFunc)EVAL(ast[0], env);
                    MalList arguments = new MalList();
                    foreach (MalVal mv in ast.rest().getValue())
                    {
                        arguments.conj_BANG(EVAL(mv, env));
                    }
                    MalVal fnast = f.getAst();
                    if (fnast != null)
                    {
                        orig_ast = fnast;
                        env      = f.genEnv(arguments);
                    }
                    else
                    {
                        return(f.apply(arguments));
                    }
                    break;
                }
            }
        }