12.3E-15, 12.3E5

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12.3E-15, 12.3E5 ,,, gt, , while,
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2
(2)1????(???????)

• VB??????1????
• ?1??1?????
• ?1??????????()????
• ???????????????????(_)????????
• ???????????????()

3
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4
??(1)

• Private Alltext As String
• Private ScanMode As Short
• Private Function scanComment() As String
• Dim CH1, CH2 As String Dim LN As
  Integer
• CH1 Microsoft.VisualBasic.Left(Alltext,
  1)
• Select Case ScanMode
• Case 0
• CH2 Microsoft.VisualBasic.Left(A
  lltext, 2)
• If CH1 " " Or CH1 " " Or CH1
  vbTab Then
• LN Microsoft.VisualBasic.Len
  (Alltext)
• Alltext Microsoft.VisualBasi
  c.Right(Alltext, LN - 1)
• scanComment " "
• ElseIf CH2 vbCrLf Then
• LN Microsoft.VisualBasic.Len
  (Alltext)
• Alltext Microsoft.VisualBasi
  c.Right(Alltext, LN - 2)
• scanComment " "
• ElseIf CH2 "//" Then
• LN Microsoft.VisualBasic.Len
  (Alltext)
• Alltext Microsoft.VisualBasi
  c.Right(Alltext, LN - 2)

5
??(2)

• ElseIf CH2 "/" Then
• LN Microsoft.VisualBasic.Len
  (Alltext)
• Alltext Microsoft.VisualBasi
  c.Right(Alltext, LN - 2)
• Do While Alltext ltgt ""
• CH2 Microsoft.VisualBasi
  c.Left(Alltext, 2)
• If CH2 "/" Then
• LN
  Microsoft.VisualBasic.Len(Alltext)
• Alltext
  Microsoft.VisualBasic.Right(Alltext, LN - 2)
• Exit Do
• End If
• LN Microsoft.VisualBasic
  .Len(Alltext)
• Alltext
  Microsoft.VisualBasic.Right(Alltext, LN - 1)
• Loop
• scanComment " "
• Else
• scanComment CH1
• LN Microsoft.VisualBasic.Len
  (Alltext)
• Alltext Microsoft.VisualBasi
  c.Right(Alltext, LN - 1)
• If CH1 """" Then

6
??(3)

• If CH1 """" Then
• ScanMode 0
• ElseIf CH1 "\" Then
• ScanMode 3
• End If
• Case 2
• scanComment CH1
• LN Microsoft.VisualBasic.Len(All
  text)
• Alltext Microsoft.VisualBasic.Ri
  ght(Alltext, LN - 1)
• ScanMode 0
• Case 3
• scanComment CH1
• LN Microsoft.VisualBasic.Len(All
  text)
• Alltext Microsoft.VisualBasic.Ri
  ght(Alltext, LN - 1)
• ScanMode 1
• End Select
• End Function
• Private Sub Button2_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles Button2.Click
• Dim R, Str As String

7
(3)??????

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8
C?????????(??1)

• Private Function setWordData(ByVal tp As String,
  ByVal st As String) As WordData
• setWordData.Type tp
• setWordData.Str st
• End Function
• Private Function setString()
• Dim Str, R As String
• Str """" R scanComment()
• Do While R ltgt """"
• If R "\" Then
• Str Str R R scanComment()
• If R "" Then
• MsgBox("????????????????????")
  
• R """"
• Exit Do
• End If
• End If
• Str Str R R scanComment()
• Loop
• setString Str R

9
C?????????(??2)

• Private Function setChar()
• Dim Str, R As String
• Str "'" R scanComment()
• Do While R ltgt "'"
• If R "\" Then
• Str Str R R scanComment()
• If R "" Then
• MsgBox("????????????????????")
  
• R "'"
• Exit Do
• End If
• End If
• Str Str R R scanComment()
• Loop
• setChar Str R
• End Function

10
C?????????(??3)

• Private Function setNumber(ByVal RR As String)
• Dim Str, R As String R RR
• If R ltgt "." Then
• Str RR R scanComment()
• Do While Asc(R) gt Asc("0") And
  Asc(R) lt Asc("9")
• Str Str R R scanComment()
• Loop
• If R ltgt "." Then
• Alltext R Alltext setNumber
  Str
• Exit Function
• End If
• End If
• Str Str R R scanComment()
• Do While Asc(R) gt Asc("0") And Asc(R) lt
  Asc("9")
• Str Str R R scanComment()
• Loop
• Alltext R Alltext
• setNumber Str
• End Function

11
C?????????(??4)

• Private Function setName(ByVal RR As String)
• Dim Str, R As String
• R RR Str RR R scanComment()
• Do While (Asc(R) gt Asc("A") And Asc(R)
  lt Asc("Z")) Or _
• (Asc(R) gt Asc("a") And Asc(R)
  lt Asc("z")) Or _
• (Asc(R) gt Asc("0") And Asc(R)
  lt Asc("9")) Or R "_"
• Str Str R
• R scanComment()
• Loop
• Alltext R Alltext
• setName Str
• End Function

12
C?????????(??4)

• Private Function LA0() As WordData
• Dim R, Str As String Str "" ScanMode
  0 R scanComment()
• Do While Alltext ltgt "" And (R " " Or R
  "")
• R scanComment()
• Loop
• If (R " " Or R "") And Alltext ""
  Then
• LA0.Type "EOF LA0.Str ""
• ElseIf R """" Then
• LA0.Type "String LA0.Str
  setString()
• ElseIf R "'" Then
• LA0.Type "Char LA0.Str
  setChar()
• ElseIf R "\" Then
• LA0.Type "Code LA0.Str R
  scanComment()
• ElseIf R "." Then
• LA0.Type "Number LA0.Str
  setNumber(R)
• If LA0.Str "." Then LA0.Type "Delimiter"
• ElseIf Asc(R) gt Asc("0") And Asc(R) lt
  Asc("9") Then
• LA0.Type "Number LA0.Str
  setNumber(R)
• ElseIf (Asc(R) gt Asc("A") And Asc(R) lt
  Asc("Z")) Or _

13
C?????????(??5)

• Private Sub Button3_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles Button3.Click
• Dim S As WordData
• Alltext TextBox1.Text
• TextBox2.Text ""
• Do While Alltext ltgt ""
• S LA0()
• TextBox2.Text TextBox2.Text
  vbCrLf S.Type " Value""" S.Str """"
• Loop
• End Sub
• End Class

14
(4)?????????????

• ????????????123.5E-23???34.E5?????
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• ???34.?? ???E5?
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• ???0?? ???X0FEC?
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• ?2????????????????????(BASIC???)
• select case, end if, do while, loop until,

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15
C??????(??1)

• private bool E_exp(string str) // Elt???gt?????
• if(str.Lengthlt2) return false
• if(str0!'E' str0!'e') return false
• for(int i1iltstr.Lengthi)
  if(????(??,stri)lt0) return false
• return true
• private void set_TokenX(string type, string str)
  // ????????
• tokenXnumTokenX.typetype
• tokenXnumTokenX.strstr
• numTokenX
• private void combineDelimiter(string str1, string
  str2) // ????????
• set_TokenX("Delimiter",str1str2)

16
C??????(??2)

• private void LA1()
• numTokenX0 WordData token1,token2,token3,toke
  n4
• token1LA0()token2LA0()token3LA0()token4LA
  0() // ???
• while(token1.type!"End")
• if( token1.type"Number"
  token2.type"Name" token2.str"E"
• token3.type"Delimiter" (token3.str""
  token3.str"-")
• token4.type"Number")
• set_TokenX("Number",token1.strtoken2.strto
  ken3.strtoken4.str)
• token1LA0()token2LA0()token3LA0()toke
  n4LA0()
• else if( token1.type"Number"
  token2.type"Name" E_exp(token2.str))
• set_TokenX("Number",token1.strtoken2.str)
  
• token1token3token2token4token3LA0()tok
  en4LA0()
• else if(token1.type"Delimiter"
  token1.str"gt"
• token2.type"Delimiter"
  token2.str"" )
• combineDelimiter(token1.str,token2.str)
• token1token3token2token4token3LA0()tok
  en4LA0()

17
(5)1?????????????????

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• (??????????????????)
• FORTRAN, BASIC, COBOL

SA
LA1
1????
1?????
LA0
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ALGOL,PL/I, C, C,JAVA, C
SA
LA1
LA0
1?????