vb/step2_eval.vb

   1 Imports System
   2 Imports System.IO
   3 Imports System.Collections.Generic
   4 Imports Mal
   5 Imports MalVal = Mal.types.MalVal
   6 Imports MalInt = Mal.types.MalInt
   7 Imports MalSymbol = Mal.types.MalSymbol
   8 Imports MalList = Mal.types.MalList
   9 Imports MalVector = Mal.types.MalVector
  10 Imports MalHashMap = Mal.types.MalHashMap
  11 Imports MalFunc = Mal.types.MalFunc
  12
  13 Namespace Mal
  14     Class step2_eval
  15         ' read
  16         Shared Function READ(str As String) As MalVal
  17             Return reader.read_str(str)
  18         End Function
  19
  20         ' eval
  21         Shared Function eval_ast(ast As MalVal, env As Dictionary(Of String, MalVal)) As MalVal
  22             If TypeOf ast Is MalSymbol Then
  23                 Dim sym As MalSymbol = DirectCast(ast, MalSymbol)
  24                 return env.Item(sym.getName())
  25             Else If TypeOf ast Is MalList Then
  26                 Dim old_lst As MalList = DirectCast(ast, MalList)
  27                 Dim new_lst As MalList
  28                 If ast.list_Q() Then
  29                     new_lst = New MalList
  30                 Else
  31                     new_lst = DirectCast(New MalVector, MalList)
  32                 End If
  33                 Dim mv As MalVal
  34                 For Each mv in old_lst.getValue()
  35                     new_lst.conj_BANG(EVAL(mv, env))
  36                 Next
  37                 return new_lst
  38             Else If TypeOf ast Is MalHashMap Then
  39                 Dim new_dict As New Dictionary(Of String, MalVal)
  40                 Dim entry As KeyValuePair(Of String, MalVal)
  41                 For Each entry in DirectCast(ast,MalHashMap).getValue()
  42                     new_dict.Add(entry.Key, EVAL(DirectCast(entry.Value,MalVal), env))
  43                 Next
  44                 return New MalHashMap(new_dict)
  45             Else
  46                 return ast
  47             End If
  48             return ast
  49         End Function
  50
  51         Shared Function EVAL(orig_ast As MalVal, env As Dictionary(Of String, MalVal)) As MalVal
  52             'Console.WriteLine("EVAL: {0}", printer._pr_str(orig_ast, true))
  53             If not orig_ast.list_Q() Then
  54                 return eval_ast(orig_ast, env)
  55             End If
  56
  57             ' apply list
  58             Dim ast As MalList = DirectCast(orig_ast, MalList)
  59             If ast.size() = 0  Then
  60                 return ast
  61             End If
  62             Dim a0 As MalVal = ast(0)
  63             Dim el As MalList = DirectCast(eval_ast(ast, env), MalList)
  64             Dim f As MalFunc = DirectCast(el(0), MalFunc)
  65             Return f.apply(el.rest())
  66         End Function
  67
  68         ' print
  69         Shared Function PRINT(exp As MalVal) As String
  70             return printer._pr_str(exp, TRUE)
  71         End Function
  72
  73         ' repl
  74         Shared repl_env As Dictionary(Of String, MalVal)
  75
  76         Shared Function REP(str As String) As String
  77             Return PRINT(EVAL(READ(str), repl_env))
  78         End Function
  79
  80         Shared Function add(a As MalList) As MalVal
  81             Return DirectCast(a.Item(0),MalInt) + DirectCast(a.Item(1),MalInt)
  82         End Function
  83
  84         Shared Function minus(a As MalList) As MalVal
  85             Return DirectCast(a.Item(0),MalInt) - DirectCast(a.Item(1),MalInt)
  86         End Function
  87
  88         Shared Function mult(a As MalList) As MalVal
  89             Return DirectCast(a.Item(0),MalInt) * DirectCast(a.Item(1),MalInt)
  90         End Function
  91
  92         Shared Function div(a As MalList) As MalVal
  93             Return DirectCast(a.Item(0),MalInt) / DirectCast(a.Item(1),MalInt)
  94         End Function
  95
  96         Shared Function Main As Integer
  97             Dim args As String() = Environment.GetCommandLineArgs()
  98
  99             repl_env = New Dictionary(Of String, MalVal)
 100             repl_env.Add("+", New MalFunc(AddressOf add))
 101             repl_env.Add("-", New MalFunc(AddressOf minus))
 102             repl_env.Add("*", New MalFunc(AddressOf mult))
 103             repl_env.Add("/", New MalFunc(AddressOf div))
 104
 105
 106             If args.Length > 1 AndAlso args(1) = "--raw" Then
 107                 Mal.readline.SetMode(Mal.readline.Modes.Raw)
 108             End If
 109
 110             ' repl loop
 111             Dim line As String
 112             Do
 113                 Try
 114                     line = Mal.readline.Readline("user> ")
 115                     If line is Nothing Then
 116                         Exit Do
 117                     End If
 118                     If line = "" Then
 119                         Continue Do
 120                     End If
 121                 Catch e As IOException
 122                     Console.WriteLine("IOException: " & e.Message)
 123                 End Try
 124                 Try
 125                     Console.WriteLine(REP(line))
 126                 Catch e as Exception
 127                     Console.WriteLine("Error: " & e.Message)
 128                     Console.WriteLine(e.StackTrace)
 129                     Continue Do
 130                 End Try
 131             Loop While True
 132         End function
 133     End Class
 134 End Namespace