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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.

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

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You may use Boost Spirit [^].
For your simple case adapting the calc5 sample [^] to add some constants should not be too difficult.
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Thank you all for your helpful responses. I've found Expression evaluator : using RPN[^]
It's useful and simple.
Thanks again.
Best regards
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