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Small Basic Sample: Line Editor

This sample is for File.InsertLine, File.ReadLine, and File.WriteLine.

Usage

Enter the text file name to edit. H command shows the help.

Code

' Line Editor
' Version 0.1
' Copyright © 2017 Nonki Takahashi. The MIT License.
 
' Known Issues
' [1] Can't display Unicode characters.
' [2] Can't delete lines.
 
Init()
While cont
  ShowPrompt()
  ReadCommand()
  DoCommand()
EndWhile
Program.End()
 
Sub DoCommand
  If cmd =  "h" Or cmd = "?"  Then
    TextWindow.WriteLine("?|h - help")
    TextWindow.WriteLine("i[<l1>,<l2>] - insert line[s] to file")
    TextWindow.WriteLine("l[<l1>,<l2>|*] - list lines")
    TextWindow.WriteLine("m<l> - move to a line")
    TextWindow.WriteLine("q - quit")
    TextWindow.WriteLine("r[<l1>,<l2>] - replace line[s] to file")
  ElseIf cmd =  "i" Then
    If maxlno +  1 < l1 Then
      For l =  maxlno + 1 To l1 - 1
        File.WriteLine(filename, l, "")
      EndFor
    EndIf
    For l =  l1 To l2
      line = TextWindow.Read()
      File.InsertLine(filename, l, line)
    EndFor
    maxlno = maxlno  + l2 - l1 +  1
  ElseIf cmd =  "l" Then
    For l =  l1 To l2
      sp = Text.GetSubText(" ", 1, Text.GetLength(l2) - Text.GetLength(l))
      line = File.ReadLine(filename, l)
      TextWindow.WriteLine(sp + l  + " " + line)
    EndFor
  ElseIf cmd =  "m" Then
    If maxlno <  l1 Then
      curlno = maxlno
    Else
      curlno = l1
    EndIf
  ElseIf cmd =  "q" Then
    cont = "False"
  ElseIf cmd =  "r" Then
    If 1 <= l1 And  l1 <= l2 And  l2 <= maxlno Then
      For l =  l1 To l2
        line = TextWindow.Read()
        File.WriteLine(filename, l, line)
      EndFor
    Else
      msg = "Invalid lines: " + l1  + "," + l2
      ShowError()
    EndIf
  Else
    msg = "Unknown cmd: " + cmd
    ShowError()
  EndIf
EndSub
 
Sub GetCommand
  ' param cmdline - command line
  ' param p - pointer to command line
  ' return p - updated pointer to command line
  ' return cmd - command
  cmd = ""
  c = Text.ConvertToLowerCase(Text.GetSubText(cmdline, p, 1))
  If Text.IsSubText("abcdefghijklmnopqrstuvwxyz?", c) Then 
    cmd = c
    p = p  + 1
  EndIf
EndSub
 
Sub GetDelim
  ' param cmdline - command line
  ' param p - pointer to command line
  ' return p - updated pointer to command line
  ' return delim - delimiter
  delim = ""
  c = Text.GetSubText(cmdline, p, 1)
  If c =  "," Then
    delim = c
    p = p  + 1
  EndIf
EndSub
 
Sub GetLineNo
  ' param cmdline - command line
  ' param p - pointer to command line
  ' return p - updated pointer to command line
  ' return l1 - start line number
  ' return l2 - end line number
  c = Text.GetSubText(cmdline, p, 1)
  If c =  "*" Then
    l1 = 1
    l2 = maxlno
  Else
    GetNum()
    If n =  "" Then
      l1 = curlno
    Else
      l1 = n
    EndIf
    SkipSpace()
    GetDelim()
    If delim =  "" Then
      l2 = l1
    Else
      SkipSpace()
      GetNum()
      If n =  "" Then
        l2 = l1
      Else
        l2 = n
      EndIf
    EndIf
  EndIf
EndSub
 
Sub GetMaxLineNo
  ' param filename
  ' return maxlno - max line number
  maxlno = 0
  buf = File.ReadContents(filename)
  p = 1
  len = Text.GetLength(buf)
  While p <  len
    maxlno = maxlno  + 1
    eol = Text.GetIndexOf(Text.GetSubTextToEnd(buf, p), LF)
    If eol =  0 Then
      p = len
    Else
      p = p  + eol
    EndIf
  EndWhile
EndSub
 
Sub GetNum
  ' param cmdline - command line
  ' param p - pointer to command line
  ' return p - updated pointer to command line
  ' return n - number
  n = ""
  c = Text.GetSubText(cmdline, p, 1)
  While Text.IsSubText("0123456789", c)
    n = Text.Append(n, c)
    p = p  + 1
    c = Text.GetSubText(cmdline, p, 1)
  EndWhile
EndSub
 
Sub Init
  Not = "False=True;True=False;"
  cont = "True"
  LF = Text.GetCharacter(10)
  If 0 <  Program.ArgumentCount Then
    filename = Program.GetArgument(1)
  EndIf
  While filename =  ""
    TextWindow.Write("Filename? ")
    filename = TextWindow.Read()
  EndWhile
  If Not[Text.IsSubText(filename, "\")] Then
    filename = Program.Directory + "\"  + filename
  EndIf
  GetMaxLineNo()
  TextWindow.WriteLine(maxlno + " lines")
  curlno = 1
EndSub
 
Sub ReadCommand
  cmdline = TextWindow.Read()
  p = 1
  SkipSpace()
  GetCommand()
  SkipSpace()
  GetLineNo()
EndSub
 
Sub ShowError
  ' param msg - error message
  TextWindow.ForegroundColor = "Red"
  TextWindow.WriteLine(msg)
  TextWindow.ForegroundColor = "Gray"
EndSub
 
Sub ShowPrompt
  TextWindow.Write("> ")
EndSub
 
Sub SkipSpace
  ' param cmdline - command line
  ' param p - pointer to command line
  ' return p - updated pointer to command line
  c = Text.GetSubText(cmdline, p, 1)
  While c =  " "
    p = p  + 1
    c = Text.GetSubText(cmdline, p, 1)
  EndWhile
EndSub

See Also