HP Forum Archive 19

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Parsing Object Oriented Expressions with RPN Message #1 Posted by Howard Owen on 5 Oct 2010, 1:39 a.m. Incredibly geeky hyperlink.

Re: Parsing Object Oriented Expressions with RPN Message #2 Posted by Bill Zimmerly on 5 Oct 2010, 3:07 a.m., in response to message #1 by Howard Owen Very cool Howard, thanks for posting it. ;)

Re: Parsing Object Oriented Expressions with RPN Message #3 Posted by David Hayden on 5 Oct 2010, 6:18 a.m., in response to message #1 by Howard Owen For what it's worth, this is basically how an algebraic calculator evaluates an expression that you type. So in a way, even TI's are RPN at heart :). HP calculators do the same thing when they parse a symbolic expression because symbolics are stored in postfix notation.

Re: Parsing Object Oriented Expressions with RPN Message #4 Posted by Thomas Klemm on 5 Oct 2010, 12:57 p.m., in response to message #3 by David Hayden Quote: symbolics are stored in postfix notation. That's why you can't enter something like '(A+B)'. It is stored as 'A B +' and displayed as 'A+B'. BTW: There's a programm ->RPN in the directory 'EXAMPLE/PRGS' you get when executing the command TEACH. It transforms an algebraic expression to its equivalent RPN-representation. Thomas Edited: 5 Oct 2010, 12:59 p.m.

Re: Parsing Object Oriented Expressions with RPN Message #5 Posted by Namir on 6 Oct 2010, 2:03 a.m., in response to message #1 by Howard Owen Several years ago I wrote an expression parser that converts an algebraic expression (with variables and functions) into an array of RPN tokens. This approach allows the re-evaluation of the expression multiple times without having to re-parse each time. It was a fun project in VB .Net. The program's GUI would list the parsed RPN expression. Namir Edited: 6 Oct 2010, 2:04 a.m.

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