path: root/cs/step8_macros.cs

using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using Mal;
using MalVal = Mal.types.MalVal;
using MalString = Mal.types.MalString;
using MalSymbol = Mal.types.MalSymbol;
using MalInt = Mal.types.MalInt;
using MalList = Mal.types.MalList;
using MalVector = Mal.types.MalVector;
using MalHashMap = Mal.types.MalHashMap;
using MalFunc = Mal.types.MalFunc;
using Env = Mal.env.Env;

namespace Mal {
    class step8_macros {
        // read
        static MalVal READ(string str) {
            return reader.read_str(str);
        }

        // eval
        public static bool is_pair(MalVal x) {
            return x is MalList && ((MalList)x).size() > 0;
        }

        public static MalVal quasiquote(MalVal ast) {
            if (!is_pair(ast)) {
                return new MalList(new MalSymbol("quote"), ast);
            } else {
                MalVal a0 = ((MalList)ast)[0];
                if ((a0 is MalSymbol) &&
                    (((MalSymbol)a0).getName() == "unquote")) {
                    return ((MalList)ast)[1];
                } else if (is_pair(a0)) {
                    MalVal a00 = ((MalList)a0)[0];
                    if ((a00 is MalSymbol) &&
                        (((MalSymbol)a00).getName() == "splice-unquote")) {
                        return new MalList(new MalSymbol("concat"),
                                           ((MalList)a0)[1],
                                           quasiquote(((MalList)ast).rest()));
                    }
                }
                return new MalList(new MalSymbol("cons"),
                                   quasiquote(a0),
                                   quasiquote(((MalList)ast).rest()));
            }
        }

        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;
        }

        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;
        }

        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;
            }
        }


        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 expanded; } 
            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 "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;
            }

            }
        }

        // print
        static string PRINT(MalVal exp) {
            return printer._pr_str(exp, true);
        }

        // repl
        static void Main(string[] args) {
            var repl_env = new Mal.env.Env(null);
            Func<string, MalVal> RE = (string str) => EVAL(READ(str), repl_env);
            
            // core.cs: defined using C#
            foreach (var entry in core.ns) {
                repl_env.set(new MalSymbol(entry.Key), entry.Value);
            }
            repl_env.set(new MalSymbol("eval"), new MalFunc(
                        a => EVAL(a[0], repl_env)));
            int fileIdx = 1;
            if (args.Length > 0 && args[0] == "--raw") {
                Mal.readline.mode = Mal.readline.Mode.Raw;
                fileIdx = 2;
            }
            MalList _argv = new MalList();
            for (int i=fileIdx; i < args.Length; i++) {
                _argv.conj_BANG(new MalString(args[i]));
            }
            repl_env.set(new MalSymbol("*ARGV*"), _argv);

            // core.mal: defined using the language itself
            RE("(def! not (fn* (a) (if a false true)))");
            RE("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))");
            RE("(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)))))))");
            RE("(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))))))))");

            if (args.Length > fileIdx) {
                RE("(load-file \"" + args[fileIdx] + "\")");
                return;
            }

            // repl loop
            while (true) {
                string line;
                try {
                    line = Mal.readline.Readline("user> ");
                    if (line == null) { break; }
                    if (line == "") { continue; }
                } catch (IOException e) {
                    Console.WriteLine("IOException: " + e.Message);
                    break;
                }
                try {
                    Console.WriteLine(PRINT(RE(line)));
                } catch (Mal.types.MalContinue) {
                    continue;
                } catch (Exception e) {
                    Console.WriteLine("Error: " + e.Message);
                    Console.WriteLine(e.StackTrace);
                    continue;
                }
            }
        }
    }
}