Evaluate dynamic formule

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Hello everyone, I'm writing a C++ application.
In my application I must load a formule typied by the user from a text file.
The formule can be ((WIDHT+5)*5/2)-(LARG/2). The problem is that that formule is a string and I've found how I can evaluate it as a double. Knowing that WIDTH and LARG are constant.
Thanks for your precious help
Best regards.

Posted 1-Apr-10 23:15pm

hedfi.mourad

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CPallini · Answer 1 · 2010-04-01T23:19:00

Solution 1

If you need to evaluate expressions, then you may consider to embed a scripting launguage (e.g. Lua, see, for instance [^]) in you application.
:)

Posted 1-Apr-10 23:19pm

CPallini

Updated 1-Apr-10 23:20pm

v2

Luc Pattyn · Answer 2 · 2010-04-02T03:40:00

Solution 2

What you need is code to evaluate an expression; there are several good articles on the subject here at CodeProject, e.g. State of the Art Expression Evaluation[^]

:)

Posted 2-Apr-10 3:40am

Luc Pattyn

Alain Rist · Answer 3 · 2010-04-02T04:20:00

Solution 3

You may use Boost Spirit [^].
For your simple case adapting the calc5 sample [^] to add some constants should not be too difficult.
cheers,
AR

Posted 2-Apr-10 4:20am

Alain Rist

hedfi.mourad · Answer 4 · 2010-04-05T00:05:00

Solution 4

Thank you all for your helpful responses. I've found Expression evaluator : using RPN[^]
It's useful and simple.
Thanks again.
Best regards

Posted 5-Apr-10 0:05am

hedfi.mourad