vb/reader.vb

   1 Imports System
   2 Imports System.Collections
   3 Imports System.Collections.Generic
   4 Imports System.Text.RegularExpressions
   5 Imports Mal
   6 Imports MalVal = Mal.types.MalVal
   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 MalThrowable = Mal.types.MalThrowable
  12 Imports MalContinue = Mal.types.MalContinue
  13
  14 Namespace Mal
  15     Public Class reader
  16         Public Class ParseError
  17             Inherits MalThrowable
  18             Public Sub New(msg As String)
  19                 MyBase.New(msg)
  20             End Sub
  21         End Class
  22
  23         Public Class Reader
  24             Private tokens As New List(Of String)
  25             Private position As Int32 = 0
  26             Sub New(t As List(Of String))
  27                 tokens = t
  28                 position = 0
  29             End Sub
  30
  31             Public Function peek() As String
  32                 If position >= tokens.Count Then
  33                     return Nothing
  34                 Else
  35                     return tokens(position)
  36                 End If
  37             End Function
  38
  39             Public Function get_next() As String
  40                 If position >= tokens.Count Then
  41                     return Nothing
  42                 Else
  43                     position += 1
  44                     return tokens(position-1)
  45                 End If
  46             End Function
  47         End Class
  48
  49         Shared Function tokenize(str As String) As List(Of String)
  50             Dim tokens As New List(Of String)
  51             Dim pattern As String = "[\s ,]*(~@|[\[\]{}()'`~@]|""(?:[\\].|[^\\""])*""|;.*|[^\s \[\]{}()'""`~@,;]*)"
  52             Dim regex As New Regex(pattern)
  53             For Each match As Match In regex.Matches(str)
  54                 Dim token As String = match.Groups(1).Value
  55                 If Not token Is Nothing _
  56                     AndAlso Not token = "" _
  57                     AndAlso Not token(0) = ";" Then
  58                     'Console.WriteLine("match: ^" & match.Groups[1] & "$")
  59                     tokens.Add(token)
  60                 End If
  61             Next
  62             return tokens
  63         End Function
  64
  65         Shared Function read_atom(rdr As Reader) As MalVal
  66             Dim token As String = rdr.get_next()
  67             Dim pattern As String = "(^-?[0-9]+$)|(^-?[0-9][0-9.]*$)|(^nil$)|(^true$)|(^false$)|^("".*"")$|^:(.*)|(^[^""]*$)"
  68             Dim regex As Regex = New Regex(pattern)
  69             Dim match As Match = regex.Match(token)
  70             'Console.WriteLine("token: ^" + token + "$")
  71             If not match.Success Then
  72                 throw New ParseError("unrecognized token '" & token & "'")
  73             End If
  74             If match.Groups(1).Value <> String.Empty Then
  75                 return New Mal.types.MalInt(Integer.Parse(match.Groups(1).Value))
  76             Else If match.Groups(3).Value <> String.Empty Then
  77                 return Mal.types.Nil
  78             Else If match.Groups(4).Value <> String.Empty Then
  79                 return Mal.types.MalTrue
  80             Else If match.Groups(5).Value <> String.Empty Then
  81                 return Mal.types.MalFalse
  82             Else If match.Groups(6).Value <> String.Empty Then
  83                 Dim str As String = match.Groups(6).Value
  84                 return New Mal.types.MalString(
  85                         str.Substring(1, str.Length-2) _
  86                         .Replace("\""", """") _
  87                         .Replace("\n", Environment.NewLine) _
  88                         .Replace("\\", "\"))
  89             Else If match.Groups(7).Value <> String.Empty Then
  90                 return New Mal.types.MalString(ChrW(&H029e) & match.Groups(7).Value)
  91             Else If match.Groups(8).Value <> String.Empty Then
  92                 return New Mal.types.MalSymbol(match.Groups(8).Value)
  93             Else
  94                 throw New ParseError("unrecognized '" & match.Groups(0).Value & "'")
  95             End If
  96         End Function
  97
  98         Shared Function read_list(rdr As Reader, lst As MalList,
  99                                   start As String, last As String) As MalVal
 100             Dim token As String = rdr.get_next()
 101             If token(0) <> start Then
 102                 throw New ParseError("expected '" & start & "'")
 103             End If
 104
 105             token = rdr.peek()
 106             While token IsNot Nothing AndAlso token(0) <> last
 107                 lst.conj_BANG(read_form(rdr))
 108                 token = rdr.peek()
 109             End While
 110
 111             If token Is Nothing Then
 112                 throw New ParseError("expected '" & last & "', got EOF")
 113             End If
 114             rdr.get_next()
 115
 116             return lst
 117         End Function
 118
 119         Shared Function read_hash_map(rdr As Reader) As MalVal
 120             Dim lst As MalList = DirectCast(read_list(rdr, new MalList(),
 121                                                       "{", "}"),MalList)
 122             return New MalHashMap(lst)
 123         End Function
 124
 125
 126         Shared Function read_form(rdr As Reader) As MalVal
 127             Dim token As String = rdr.peek()
 128             If token Is Nothing Then
 129                 throw New MalContinue()
 130             End If
 131             Dim form As MalVal = Nothing
 132
 133             Select token
 134             Case "'"
 135                 rdr.get_next()
 136                 return New MalList(New MalSymbol("quote"),
 137                                    read_form(rdr))
 138             Case "`"
 139                 rdr.get_next()
 140                 return New MalList(New MalSymbol("quasiquote"),
 141                                    read_form(rdr))
 142             Case "~"
 143                 rdr.get_next()
 144                 return New MalList(New MalSymbol("unquote"),
 145                                    read_form(rdr))
 146             Case "~@"
 147                 rdr.get_next()
 148                 return new MalList(New MalSymbol("splice-unquote"),
 149                                    read_form(rdr))
 150             Case "^"
 151                 rdr.get_next()
 152                 Dim meta As MalVal = read_form(rdr)
 153                 return new MalList(New MalSymbol("with-meta"),
 154                                    read_form(rdr),
 155                                    meta)
 156             Case "@"
 157                 rdr.get_next()
 158                 return new MalList(New MalSymbol("deref"),
 159                                    read_form(rdr))
 160
 161             Case "("
 162                 form = read_list(rdr, New MalList(), "(" , ")")
 163             Case ")"
 164                 throw New ParseError("unexpected ')'")
 165             Case "["
 166                 form = read_list(rdr, New MalVector(), "[" , "]")
 167             Case "]"
 168                 throw New ParseError("unexpected ']'")
 169             Case "{"
 170                 form = read_hash_map(rdr)
 171             Case "}"
 172                 throw New ParseError("unexpected '}'")
 173             Case Else
 174                 form = read_atom(rdr)
 175             End Select
 176             return form
 177         End Function
 178
 179
 180         Shared Function read_str(str As string) As MalVal
 181             return read_form(New Reader(tokenize(str)))
 182         End Function
 183     End Class
 184 End Namespace