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Imports System
Imports System.Collections
Imports System.Collections.Generic
Imports System.Text.RegularExpressions
Imports Mal
Imports MalVal = Mal.types.MalVal
Imports MalSymbol = Mal.types.MalSymbol
Imports MalList = Mal.types.MalList
Imports MalVector = Mal.types.MalVector
Imports MalHashMap = Mal.types.MalHashMap
Imports MalThrowable = Mal.types.MalThrowable
Imports MalContinue = Mal.types.MalContinue
Namespace Mal
Public Class reader
Public Class ParseError
Inherits MalThrowable
Public Sub New(msg As String)
MyBase.New(msg)
End Sub
End Class
Public Class Reader
Private tokens As New List(Of String)
Private position As Int32 = 0
Sub New(t As List(Of String))
tokens = t
position = 0
End Sub
Public Function peek() As String
If position >= tokens.Count Then
return Nothing
Else
return tokens(position)
End If
End Function
Public Function get_next() As String
If position >= tokens.Count Then
return Nothing
Else
position += 1
return tokens(position-1)
End If
End Function
End Class
Shared Function tokenize(str As String) As List(Of String)
Dim tokens As New List(Of String)
Dim pattern As String = "[\s ,]*(~@|[\[\]{}()'`~@]|""(?:[\\].|[^\\""])*""|;.*|[^\s \[\]{}()'""`~@,;]*)"
Dim regex As New Regex(pattern)
For Each match As Match In regex.Matches(str)
Dim token As String = match.Groups(1).Value
If Not token Is Nothing _
AndAlso Not token = "" _
AndAlso Not token(0) = ";" Then
'Console.WriteLine("match: ^" & match.Groups[1] & "$")
tokens.Add(token)
End If
Next
return tokens
End Function
Shared Function read_atom(rdr As Reader) As MalVal
Dim token As String = rdr.get_next()
Dim pattern As String = "(^-?[0-9]+$)|(^-?[0-9][0-9.]*$)|(^nil$)|(^true$)|(^false$)|^("".*"")$|^:(.*)|(^[^""]*$)"
Dim regex As Regex = New Regex(pattern)
Dim match As Match = regex.Match(token)
'Console.WriteLine("token: ^" + token + "$")
If not match.Success Then
throw New ParseError("unrecognized token '" & token & "'")
End If
If match.Groups(1).Value <> String.Empty Then
return New Mal.types.MalInt(Integer.Parse(match.Groups(1).Value))
Else If match.Groups(3).Value <> String.Empty Then
return Mal.types.Nil
Else If match.Groups(4).Value <> String.Empty Then
return Mal.types.MalTrue
Else If match.Groups(5).Value <> String.Empty Then
return Mal.types.MalFalse
Else If match.Groups(6).Value <> String.Empty Then
Dim str As String = match.Groups(6).Value
return New Mal.types.MalString(
str.Substring(1, str.Length-2) _
.Replace("\""", """") _
.Replace("\n", Environment.NewLine))
Else If match.Groups(7).Value <> String.Empty Then
return New Mal.types.MalString(ChrW(&H029e) & match.Groups(7).Value)
Else If match.Groups(8).Value <> String.Empty Then
return New Mal.types.MalSymbol(match.Groups(8).Value)
Else
throw New ParseError("unrecognized '" & match.Groups(0).Value & "'")
End If
End Function
Shared Function read_list(rdr As Reader, lst As MalList,
start As String, last As String) As MalVal
Dim token As String = rdr.get_next()
If token(0) <> start Then
throw New ParseError("expected '" & start & "'")
End If
token = rdr.peek()
While token IsNot Nothing AndAlso token(0) <> last
lst.conj_BANG(read_form(rdr))
token = rdr.peek()
End While
If token Is Nothing Then
throw New ParseError("expected '" & last & "', got EOF")
End If
rdr.get_next()
return lst
End Function
Shared Function read_hash_map(rdr As Reader) As MalVal
Dim lst As MalList = DirectCast(read_list(rdr, new MalList(),
"{", "}"),MalList)
return New MalHashMap(lst)
End Function
Shared Function read_form(rdr As Reader) As MalVal
Dim token As String = rdr.peek()
If token Is Nothing Then
throw New MalContinue()
End If
Dim form As MalVal = Nothing
Select token
Case "'"
rdr.get_next()
return New MalList(New MalSymbol("quote"),
read_form(rdr))
Case "`"
rdr.get_next()
return New MalList(New MalSymbol("quasiquote"),
read_form(rdr))
Case "~"
rdr.get_next()
return New MalList(New MalSymbol("unquote"),
read_form(rdr))
Case "~@"
rdr.get_next()
return new MalList(New MalSymbol("splice-unquote"),
read_form(rdr))
Case "^"
rdr.get_next()
Dim meta As MalVal = read_form(rdr)
return new MalList(New MalSymbol("with-meta"),
read_form(rdr),
meta)
Case "@"
rdr.get_next()
return new MalList(New MalSymbol("deref"),
read_form(rdr))
Case "("
form = read_list(rdr, New MalList(), "(" , ")")
Case ")"
throw New ParseError("unexpected ')'")
Case "["
form = read_list(rdr, New MalVector(), "[" , "]")
Case "]"
throw New ParseError("unexpected ']'")
Case "{"
form = read_hash_map(rdr)
Case "}"
throw New ParseError("unexpected '}'")
Case Else
form = read_atom(rdr)
End Select
return form
End Function
Shared Function read_str(str As string) As MalVal
return read_form(New Reader(tokenize(str)))
End Function
End Class
End Namespace
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