vb/step5_tco.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 Imports MalEnv = Mal.env.Env
  13
  14 Namespace Mal
  15     Class step5_tco
  16         ' read
  17         Shared Function READ(str As String) As MalVal
  18             Return reader.read_str(str)
  19         End Function
  20
  21         ' eval
  22         Shared Function eval_ast(ast As MalVal, env As MalEnv) As MalVal
  23             If TypeOf ast Is MalSymbol Then
  24                 return env.do_get(DirectCast(ast, MalSymbol))
  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         ' TODO: move to types.vb when it is ported
  52         Class FClosure
  53             Public ast As MalVal
  54             Public params As MalList
  55             Public env As MalEnv
  56             Function fn(args as MalList) As MalVal
  57                 return EVAL(ast, new MalEnv(env, params, args))
  58             End Function
  59         End Class
  60
  61         Shared Function EVAL(orig_ast As MalVal, env As MalEnv) As MalVal
  62             Do
  63
  64             'Console.WriteLine("EVAL: {0}", printer._pr_str(orig_ast, true))
  65             If not orig_ast.list_Q() Then
  66                 return eval_ast(orig_ast, env)
  67             End If
  68
  69             ' apply list
  70             Dim ast As MalList = DirectCast(orig_ast, MalList)
  71             If ast.size() = 0  Then
  72                 return ast
  73             End If
  74             Dim a0 As MalVal = ast(0)
  75             Dim a0sym As String
  76             If TypeOf a0 is MalSymbol Then
  77                 a0sym = DirectCast(a0,MalSymbol).getName()
  78             Else
  79                 a0sym = "__<*fn*>__"
  80             End If
  81
  82             Select a0sym
  83             Case "def!"
  84                 Dim a1 As MalVal = ast(1)
  85                 Dim a2 As MalVal = ast(2)
  86                 Dim res As MalVal = EVAL(a2, env)
  87                 env.do_set(DirectCast(a1,MalSymbol), res)
  88                 return res
  89             Case "let*"
  90                 Dim a1 As MalVal = ast(1)
  91                 Dim a2 As MalVal = ast(2)
  92                 Dim key As MalSymbol
  93                 Dim val as MalVal
  94                 Dim let_env As new MalEnv(env)
  95                 For i As Integer = 0 To (DirectCast(a1,MalList)).size()-1 Step 2
  96                     key = DirectCast(DirectCast(a1,MalList)(i),MalSymbol)
  97                     val = DirectCast(a1,MalList)(i+1)
  98                     let_env.do_set(key, EVAL(val, let_env))
  99                 Next
 100                 orig_ast = a2
 101                 env = let_env
 102             Case "do"
 103                 eval_ast(ast.slice(1, ast.size()-1), env)
 104                 orig_ast = ast(ast.size()-1)
 105             Case "if"
 106                 Dim a1 As MalVal = ast(1)
 107                 Dim cond As MalVal = EVAL(a1, env)
 108                 If cond Is Mal.types.Nil or cond Is Mal.types.MalFalse Then
 109                     ' eval false slot form
 110                     If ast.size() > 3 Then
 111                         orig_ast = ast(3)
 112                     Else
 113                         return Mal.types.Nil
 114                     End If
 115                 Else
 116                     ' eval true slot form
 117                     orig_ast = ast(2)
 118
 119                 End If
 120             Case "fn*"
 121                 Dim fc As New FClosure()
 122                 fc.ast = ast(2)
 123                 fc.params = DirectCast(ast(1),MalLIst)
 124                 fc.env = env
 125                 Dim f As Func(Of MalList, MalVal) = AddressOf fc.fn
 126                 Dim mf As new MalFunc(ast(2), env,
 127                                       DirectCast(ast(1),MalList), f)
 128                 return DirectCast(mf,MalVal)
 129             Case Else
 130                 Dim el As MalList = DirectCast(eval_ast(ast, env), MalList)
 131                 Dim f As MalFunc = DirectCast(el(0), MalFunc)
 132                 Dim fnast As MalVal = f.getAst()
 133                 If not fnast Is Nothing
 134                     orig_ast = fnast
 135                     env = f.genEnv(el.rest())
 136                 Else
 137                     Return f.apply(el.rest())
 138                 End If
 139             End Select
 140
 141             Loop While True
 142         End Function
 143
 144         ' print
 145         Shared Function PRINT(exp As MalVal) As String
 146             return printer._pr_str(exp, TRUE)
 147         End Function
 148
 149         ' repl
 150         Shared repl_env As MalEnv
 151
 152         Shared Function REP(str As String) As String
 153             Return PRINT(EVAL(READ(str), repl_env))
 154         End Function
 155
 156         Shared Function Main As Integer
 157             Dim args As String() = Environment.GetCommandLineArgs()
 158
 159             repl_env = New MalEnv(Nothing)
 160
 161             ' core.vb: defined using VB.NET
 162             For Each entry As KeyValuePair(Of String,MalVal) In core.ns()
 163                 repl_env.do_set(new MalSymbol(entry.Key), entry.Value)
 164             Next
 165
 166             ' core.mal: defined using the language itself
 167             REP("(def! not (fn* (a) (if a false true)))")
 168
 169             If args.Length > 1 AndAlso args(1) = "--raw" Then
 170                 Mal.readline.SetMode(Mal.readline.Modes.Raw)
 171             End If
 172
 173             ' repl loop
 174             Dim line As String
 175             Do
 176                 Try
 177                     line = Mal.readline.Readline("user> ")
 178                     If line is Nothing Then
 179                         Exit Do
 180                     End If
 181                     If line = "" Then
 182                         Continue Do
 183                     End If
 184                 Catch e As IOException
 185                     Console.WriteLine("IOException: " & e.Message)
 186                 End Try
 187                 Try
 188                     Console.WriteLine(REP(line))
 189                 Catch e as Exception
 190                     Console.WriteLine("Error: " & e.Message)
 191                     Console.WriteLine(e.StackTrace)
 192                     Continue Do
 193                 End Try
 194             Loop While True
 195         End function
 196     End Class
 197 End Namespace