Code archives/Algorithms/Infix to Postfix

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Infix to Postfix by Zenith
(Posted 23 years ago)
Look up Infix/Postfix on www.google.com for some information!

Basically this is a good way to convert a evaluation (without brackets) to a RPN form which can be output to a stack-machine based asm output. Nifty!
(Look up Stack machines too, if you want) 
;Example:
Print "Postfix: "+cPostFix(Input())
;End of Example

Function cPostFix$(eval$)
	Local stack$[64],sp
	
	If eval = "exit" Or eval = "" Return
	Local oper$ = "+-*/"
	Local postfix$
	For i=1 To Len(eval)
		m$ = Mid(eval,i,1)
		Select m
			Case "-","+","*","/"							; is an operator
				If sp>0
					testA = Instr(oper,stack[sp-1])			; topStack operator
					testB = Instr(oper,          m)			; newOp operator
					If testA > testB						; does topStack have higher precedence than newOp
						While sp>0
							sp=sp-1							; pop the stack
							postfix=postfix + stack[sp]
						Wend
						stack[sp] = m
						sp=sp+1
					Else
						stack[sp] = m						; otherwise push the new operator to the list
						sp=sp+1
					EndIf
				Else
					stack[sp] = m							; push new operator
					sp=sp+1
				EndIf
			Default											; is an operand
				postfix=postfix+m
		End Select
	Next
	
	While sp>0
		sp=sp-1
		postfix = postfix + stack[sp]
	Wend
	Return postfix
End Function