cs/step4_if_fn_do.cs

   1 using System;
   2 using System.IO;
   3 using System.Collections;
   4 using System.Collections.Generic;
   5 using Mal;
   6 using MalVal = Mal.types.MalVal;
   7 using MalSymbol = Mal.types.MalSymbol;
   8 using MalInteger = Mal.types.MalInteger;
   9 using MalList = Mal.types.MalList;
  10 using MalVector = Mal.types.MalVector;
  11 using MalHashMap = Mal.types.MalHashMap;
  12 using MalFunction = Mal.types.MalFunction;
  13 using Env = Mal.env.Env;
  14
  15 namespace Mal {
  16     class step4_if_fn_do {
  17         // read
  18         static MalVal READ(string str) {
  19             return reader.read_str(str);
  20         }
  21
  22         // eval
  23         static MalVal eval_ast(MalVal ast, Env env) {
  24             if (ast is MalSymbol) {
  25                 MalSymbol sym = (MalSymbol)ast;
  26                 return env.get(sym.getName());
  27             } else if (ast is MalList) {
  28                 MalList old_lst = (MalList)ast;
  29                 MalList new_lst = ast.list_Q() ? new MalList()
  30                                             : (MalList)new MalVector();
  31                 foreach (MalVal mv in old_lst.getValue()) {
  32                     new_lst.conj_BANG(EVAL(mv, env));
  33                 }
  34                 return new_lst;
  35             } else if (ast is MalHashMap) {
  36                 var new_dict = new Dictionary<string, MalVal>();
  37                 foreach (var entry in ((MalHashMap)ast).getValue()) {
  38                     new_dict.Add(entry.Key, EVAL((MalVal)entry.Value, env));
  39                 }
  40                 return new MalHashMap(new_dict);
  41             } else {
  42                 return ast;
  43             }
  44         }
  45
  46
  47         static MalVal EVAL(MalVal orig_ast, Env env) {
  48             MalVal a0, a1, a2, a3, res;
  49             MalList el;
  50             //System.out.println("EVAL: " + printer._pr_str(orig_ast, true));
  51             if (!orig_ast.list_Q()) {
  52                 return eval_ast(orig_ast, env);
  53             }
  54
  55             // apply list
  56             MalList ast = (MalList)orig_ast;
  57             if (ast.size() == 0) { return ast; }
  58             a0 = ast[0];
  59
  60             String a0sym = a0 is MalSymbol ? ((MalSymbol)a0).getName()
  61                                            : "__<*fn*>__";
  62
  63             switch (a0sym) {
  64             case "def!":
  65                 a1 = ast[1];
  66                 a2 = ast[2];
  67                 res = EVAL(a2, env);
  68                 env.set(((MalSymbol)a1).getName(), res);
  69                 return res;
  70             case "let*":
  71                 a1 = ast[1];
  72                 a2 = ast[2];
  73                 MalSymbol key;
  74                 MalVal val;
  75                 Env let_env = new Env(env);
  76                 for(int i=0; i<((MalList)a1).size(); i+=2) {
  77                     key = (MalSymbol)((MalList)a1)[i];
  78                     val = ((MalList)a1)[i+1];
  79                     let_env.set(key.getName(), EVAL(val, let_env));
  80                 }
  81                 return EVAL(a2, let_env);
  82             case "do":
  83                 el = (MalList)eval_ast(ast.rest(), env);
  84                 return el[el.size()-1];
  85             case "if":
  86                 a1 = ast[1];
  87                 MalVal cond = EVAL(a1, env);
  88                 if (cond == Mal.types.Nil || cond == Mal.types.False) {
  89                     // eval false slot form
  90                     if (ast.size() > 3) {
  91                         a3 = ast[3];
  92                         return EVAL(a3, env);
  93                     } else {
  94                         return Mal.types.Nil;
  95                     }
  96                 } else {
  97                     // eval true slot form
  98                     a2 = ast[2];
  99                     return EVAL(a2, env);
 100                 }
 101             case "fn*":
 102                 MalList a1f = (MalList)ast[1];
 103                 MalVal a2f = ast[2];
 104                 Env cur_env = env;
 105                 return new MalFunction(
 106                     args => EVAL(a2f, new Env(cur_env, a1f, args)) );
 107             default:
 108                 el = (MalList)eval_ast(ast, env);
 109                 var f = (MalFunction)el[0];
 110                 return f.apply(el.rest());
 111             }
 112         }
 113
 114         // print
 115         static string PRINT(MalVal exp) {
 116             return printer._pr_str(exp, true);
 117         }
 118
 119         // repl
 120         static MalVal RE(Env env, string str) {
 121             return EVAL(READ(str), env);
 122         }
 123
 124         static void Main(string[] args) {
 125             string prompt = "user> ";
 126
 127             // core.cs: defined using C#
 128             var repl_env = new env.Env(null);
 129             foreach (var entry in core.ns) {
 130                 repl_env.set(entry.Key, entry.Value);
 131             }
 132
 133             // core.mal: defined using the language itself
 134             RE(repl_env, "(def! not (fn* (a) (if a false true)))");
 135
 136             if (args.Length > 0 && args[0] == "--raw") {
 137                 Mal.readline.mode = Mal.readline.Mode.Raw;
 138             }
 139
 140             // repl loop
 141             while (true) {
 142                 string line;
 143                 try {
 144                     line = Mal.readline.Readline(prompt);
 145                     if (line == null) { break; }
 146                 } catch (IOException e) {
 147                     Console.WriteLine("IOException: " + e.Message);
 148                     break;
 149                 }
 150                 try {
 151                     Console.WriteLine(PRINT(RE(repl_env, line)));
 152                 } catch (Mal.types.MalContinue) {
 153                     continue;
 154                 } catch (Exception e) {
 155                     Console.WriteLine("Error: " + e.Message);
 156                     Console.WriteLine(e.StackTrace);
 157                     continue;
 158                 }
 159             }
 160         }
 161     }
 162 }