create a formula from a string

[lemon3]

Hi im doing this statistical program where i want the user
to be able to make hes own formula and pass it to the program.

i am able to get it from a jlabel to a string, but i cant use the string
as a mathematical formula..
im supposed to use tokens (so i heard),
but i dont know how ??
can anyone help me, i want to have it as simple as possibly by the way,
because i am new at java so this is a kind of learning program for me.

thanks guys and gurls

[tim]

Hello lemon3. :)

I wrote I program in C# that can parse (meaning to decode from a string) basic mathematical formulas and then calculate the answer step-by-step while keeping the order of operations correct, e.g. multiply and then add, etc. It could also handle brackets. So the user would input

1 + 5 * (1 - 3 / 3)

and the program would give

1 + 5 * (1 - 3 / 3)
= 1 + 5 * (1 - 1)
= 1 + 5 * (0)
= 1 + 5 * 0
= 1 + 0
= 1

If this is what you want to do, then it will take some time to create such a system. The parsing and execution is the hardest bit but this is still a large undertaking when starting from scratch.

Unfortunately, my code is in C#, so it would not help much.:o

[Norm]

That sounds like a difficult way to do it. Reading in an expression as a string and then parsing it is not trivial!! I'd suggest that you simplify and restrict the user input in some way so that it doesnt' require parsing. For example use a form with mulitple text input areas and operand selections. Or find someone else's code that will do the parsing and evaluation and use that.
There was a student looking for a project on one of the forums. Find him and see if he will do it.

Look at:
SourceForge.net: Files

[lemon3]

thanks for your help, i found some evaluation program called jel
i will try to use that one . thanks

[tim]

I'm glad to be of assistance, lemon3. :D