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Module Program Public Enum e_kind Print Lparen Rparen Plus Minus Multi Divi Assign VarName IntNum Others Endo EofToken End Enum Structure Tokenset Dim ele_kind As e_kind Dim ss As String End Structure Dim STK_SIZ As Integer = 20 Dim stack(STK_SIZ + 1) As Integer Dim stkct As Integer = 0 Dim token As Tokenset Dim buf As String = "" Dim chr_bufp As Integer = 0 Dim ch As Char Dim vari(26) As Integer Dim errflg As Boolean = False Dim endflg As Boolean = False Sub Main(args As String()) Console.WriteLine("printまたはピリオド(.)で値表示、endで終了") While True input() next_token() '以下のコメントはtoken解析の結果をデバッグするため 'While token.ele_kind <> e_kind.EofToken ' Console.Write(token.ss) ' Console.WriteLine(token.ele_kind) ' If token.ele_kind = e_kind.Endo Then ' GoTo mainbreak ' Else ' token.ss = "" ' End If ' next_token() 'End While statement() If endflg = True Then GoTo mainbreak End If If errflg = True Then Console.WriteLine("?") End If token.ss = "" End While mainbreak: Console.WriteLine("終了") End Sub Sub input() buf = Console.ReadLine chr_bufp = 0 ch = next_char() errflg = False stkct = 0 End Sub Function next_char() If chr_bufp <= buf.Length - 1 Then next_char = buf(chr_bufp) Else next_char = "" End If End Function Function isalpha(a) isalpha = If(a >= "a" And a <= "z", True, False) End Function Function isdigit(a) isdigit = If(a >= "0" And a <= "9", True, False) End Function Function strcmp(a As String, b As String) strcmp = If(a = b, True, False) End Function Function strlen(a As String) strlen = a.Length End Function Sub strcpy(ByRef reseve As String, ByVal src As String) reseve = src End Sub Sub next_token() Dim chr_pp = 0 Do ch = next_char() If ch = " " Then chr_bufp += 1 End If Loop While ch = " " If isalpha(ch) Then While isalpha(ch) token.ss = token.ss + ch chr_pp += 1 chr_bufp += 1 If chr_bufp > buf.Length - 1 Then token.ss = token.ss.Replace(vbNullChar, "") GoTo token_kind End If ch = next_char() End While ElseIf isdigit(ch) Then While isdigit(ch) token.ss &= ch chr_pp += 1 chr_bufp += 1 If chr_bufp > buf.Length - 1 Then GoTo token_kind End If ch = next_char() End While Else token.ss = ch chr_pp = 0 chr_bufp += 1 ch = next_char() End If token_kind: chr_pp = 0 If token.ss = vbNullChar Then token.ele_kind = e_kind.EofToken Return End If token.ss = token.ss.Replace(vbNullChar, "") token.ele_kind = e_kind.Others If strcmp(token.ss, "print") Then token.ele_kind = e_kind.Print token.ss = "" ElseIf strcmp(token.ss, "end") Then token.ele_kind = e_kind.Endo ElseIf token.ss = vbNullChar Then token.ele_kind = e_kind.EofToken ElseIf isdigit(token.ss(0)) Then token.ele_kind = e_kind.IntNum ElseIf strlen(token.ss) = 1 Then If isalpha(token.ss(chr_pp)) Then token.ele_kind = e_kind.VarName Else Select Case token.ss(0) Case "." : token.ele_kind = e_kind.Print Case "(" : token.ele_kind = e_kind.Lparen Case ")" : token.ele_kind = e_kind.Rparen Case "+" : token.ele_kind = e_kind.Plus Case "-" : token.ele_kind = e_kind.Minus Case "*" : token.ele_kind = e_kind.Multi Case "/" : token.ele_kind = e_kind.Divi Case "=" : token.ele_kind = e_kind.Assign End Select End If End If End Sub Sub statement() Dim save As String = "" Select Case token.ele_kind Case e_kind.Print next_token() express() If token.ele_kind <> e_kind.EofToken Then errflg = True End If If Not errflg = True Then Console.WriteLine(pop()) End If Case e_kind.Endo endflg = True Case e_kind.VarName strcpy(save, token.ss) next_token() If token.ele_kind <> e_kind.Assign Then errflg = True Return End If token.ss = "" next_token() express() If token.ele_kind <> e_kind.EofToken Then errflg = True End If If errflg = False Then letvalue(save(0), pop()) '0607試し End If Case Else errflg = True End Select End Sub Sub express() Call term() While True If token.ele_kind = e_kind.Plus Then token.ss = "" 'tamesi next_token() term() operate(e_kind.Plus) ElseIf token.ele_kind = e_kind.Minus Then token.ss = "" next_token() term() operate(e_kind.Minus) Else Return End If End While End Sub Sub term() Call factor() While True If token.ele_kind = e_kind.Multi Then token.ss = "" next_token() term() operate(e_kind.Multi) ElseIf token.ele_kind = e_kind.Divi Then token.ss = "" next_token() term() operate(e_kind.Divi) Else Return End If End While End Sub Sub factor() Select Case token.ele_kind Case e_kind.Lparen token.ss = "" next_token() express() If token.ele_kind <> e_kind.Rparen Then errflg = True Return End If Case e_kind.IntNum push(Int(token.ss)) Case e_kind.VarName push(getvalue(token.ss)) '0607試験 Case Else errflg = True Return End Select next_token() End Sub Sub operate(ByVal Ope As e_kind) Dim d1 As Integer Dim d2 As Integer d2 = pop() d1 = pop() Select Case Ope Case e_kind.Plus push(d1 + d2) Case e_kind.Minus push(d1 - d2) Case e_kind.Multi push(d1 * d2) Case e_kind.Divi If d2 = 0 Then Console.WriteLine("divide by 0") errflg = True Else push(d1 / d2) End If End Select End Sub Function getvalue(ByVal vname As Char) getvalue = vari(Asc(vname) - Asc("a"c)) End Function Sub letvalue(ByVal vname As Char, ByVal n As Integer) vari(Asc(vname) - Asc("a"c)) = n End Sub Sub push(ByVal n As Integer) If stkct + 1 > STK_SIZ Then Console.WriteLine("stack over") End Else stkct += 1 stack(stkct) = n 'stkct += 1 End If End Sub Function pop() If errflg = True Then pop = 1 Return pop End If If stkct < 1 Then Console.WriteLine("stack under") End Else pop = stack(stkct) stkct -= 1 End If End Function End Module |
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