Print "3 + 5 * 6 + 4 / 2="+calc("3 + 5 * 6 + 4 / 2") : WaitKey()

Function calc$(term$,par$="")

	;Variabeln
	term$ = Replace(term$,"pi","3,141")
	If par <> "" Then
		While Instr(par$,"=") <> 0	
			pos = Instr(par$,"=")
			
			n1$="" : i=pos-1
			While checkchar(Mid(par$,i,1)) = 3
				n1$=Mid(par$,i,1)+n1$
				i=i-1
				If i = 0 Then Exit		
			Wend
			t_start=i
			
			n2$ = "" : i = pos+1
			While (checkchar(Mid(par$,i,1)) = 1) Or (checkchar(Mid(par$,i,1)) = 2) 
				n2$=n2$+Mid(par$,i,1)
				i=i+1
				If i = Len(par$)+1 Then Exit	
			Wend
			t_end=i
			
			par = Mid(par,1,t_start) + Mid(par$,t_end,-1)
			term$ = Replace(term$,n1,n2)
		Wend	
	EndIf

	;Leerzeichen entfernen
	term$ = Replace(term$," ","")
	
	term$ = Replace(term$,"--","+")
	term$ = Replace(term$,"++","+")
	term$ = Replace(term$,"-+","-")
	term$ = Replace(term$,"+-","-")
	
	;Funktionen
	For t=0 To 4 
		Select t
			Case 0: fnk$ = "sin("
			Case 1: fnk$ = "cos("
			Case 2: fnk$ = "tan("
			Case 3: fnk$ = "sqr("
			Case 4: fnk$ = "abs("
		End Select
		While Instr(term$,fnk$) <> 0
			pos = Instr(term$,fnk$)+Len(fnk$)
			For i = pos To Len(term)
				If(Mid(term,i,1)= ")") Then Exit
				c=c+1
			Next
				
			Select t
				Case 0: tresult$ = Sin(Float(calc(Mid(term,pos,c))))
				Case 1: tresult$ = Cos(Float(calc(Mid(term,pos,c))))
				Case 2: tresult$ = Tan(Float(calc(Mid(term,pos,c))))
				Case 3: tresult$ = Sqr(Float(calc(Mid(term,pos,c))))
				Case 4: tresult$ = Abs(Float(calc(Mid(term,pos,c))))
			End Select
			
			If Instr(tresult$,"e") <> 0 Then tresult$ = "0" 
			term = Mid(term,1,pos-1-Len(fnk$))+tresult+Mid(term,pos+c+1,-1)
		Wend
	Next
	
	term$ = Replace(term$,"--","+")
	term$ = Replace(term$,"++","+")
	term$ = Replace(term$,"-+","-")
	term$ = Replace(term$,"+-","-")
	
	;Klammern
	While Instr(term$,"(") <> 0
		For i = 1 To Len(term)
			If(Mid(term,i,1)= "(") Then pos1 = i
		Next 
		
		c=0
		For i = pos1 To Len(term)
			c=c+1
			If(Mid(term,i,1)= ")") Then Exit
		Next
		c=c-2
								
		term$ = Mid(term$,1,pos1-1)+calc(Mid(term,pos1+1,c))+Mid(term$,pos1+c+2,-1)
	Wend	
	
	term$ = Replace(term$,"--","+")
	term$ = Replace(term$,"++","+")
	term$ = Replace(term$,"-+","-")
	term$ = Replace(term$,"+-","-")

	;Rechnung
	For j = 0 To 4 
		Select j
			Case 0 op$ = "^"
			Case 1 op$ = "/"
			Case 2 op$ = "*"
			Case 3 op$ = "-"
			Case 4 op$ = "+"
		End Select
		term$ = Replace(term$,"&","-")
		
		While Instr(term$,op$) <> 0 
			pos = Instr(term$,op$)
		
			;Erste Zahl
			n1$ = "" : i = pos-1
			If i > 0 Then
				While checkchar(Mid(term$,i,1)) = 1 
					n1$=Mid(term$,i,1)+n1$
					i=i-1
					If i = 0 Then Exit		
				Wend
				t_start = i
			EndIf
			If op$ = "-" And n1$ = "" Then term$ = Mid(term$,1,pos-1)+"&"+Mid(term$,pos+1,-1) : e=1 
			If i <> 0 Then
				If checkchar(Mid(term$,i,1)) = 2 Then n1$=Mid(term$,i,1)+n1$ : i=i-1 :t_start = i
            EndIf
			
			;Zweite Zahl
			n2$ = "" : i = pos+1
			If checkchar(Mid(term$,i,1)) = 2 Then n2$=n2$+Mid(term$,i,1) : i=i+1						
			While checkchar(Mid(term$,i,1)) = 1 
				n2$=n2$+Mid(term$,i,1)
				i=i+1
				If i = Len(term)+1 Then Exit	
			Wend
			t_end = i
			
			;Ergebnis
			If Instr(n1,"e") <> 0 Then n1 = "0"
			If Instr(n2,"e") <> 0 Then n2 = "0"
			n1 = Replace(n1,"&","-")
			n2 = Replace(n2,"&","-")
			
			Select j
				Case 0 result# = Float(n1) ^ Float(n2)
				Case 1 result# = Float(n1) / Float(n2)	
				Case 2 result# = Float(n1) * Float(n2)	
				Case 3 result# = Float(n1) - Float(n2)	
				Case 4 result# = Float(n1) + Float(n2)	
			End Select	
			
			If Instr(result,"e") <> 0 Then result = "0"		
			If e = 0 Then 
				term$ = Mid(term$,1,t_start)+Str(result#)+Mid(term$,t_end,-1)
			Else
				e=0
			EndIf
		Wend
	Next
	
	Return term
End Function

Function checkchar$(char$)
	If Asc(char)>=48 And Asc(char)<=57 Then Return 1
	If Asc(char)=44 Or Asc(char)=46 Or Asc(char)=101 Then Return 1
	If Asc(char)=45 Or Asc(char) = 38 Then Return 2
	If Asc(char)>=97 And Asc(char)<=122 Then Return 3
End Function