Evaluating a mathematical string formula.

[Wade]

Hi guys,

I am building a string in code that is a mathematical formula, based on a
lot of criteria specified by the user. Once the formula is complete, I want
to evaluate it to get a result. For example:

dim strFormula as String

strFormula = "((2 + 2) * 3) / 4) - 5"

Once I have this formula, I want to evaluate it and get the result: -2.

Any tips on how I can do this?

Also, is there a way to check if the formula is valid (i.e. I didn't miss
any parenthesis or anything)? I guess I could try to evaluate it, and stick
it in a try - catch block.

Thanks for your time and help!

Wade

 

[Cor Ligthert]

Wade,

Only a link

By Peter Bromberg
http://www.eggheadcafe.com/articles/20030908.asp

I hope it helps

Cor

 

[Guest]

Three basic options:
1. Write your own postfix/prefix based expressions evaluator
2. Use Reflection.Emit to generate a function to evaluate this formula and
then execute that
3. Use the javascript eval function. There was a example posted in response
to a similar query a week or two back in this group on how to do the exact
same thing.

Rgds,
Anand M
VB.NET MVP
http://www.dotnetindia.com

 

[Wade]

The solution from the following website proved to be the perfect solution to
my problem:

http://www.codeproject.com/vb/net/math_expression_evaluator.asp

Thanks!

 

[Herfried K. Wagner [MVP]]

I am building a string in code that is a mathematical formula, based on a
lot of criteria specified by the user. Once the formula is complete, I
want
to evaluate it to get a result. For example:

dim strFormula as String

strFormula = "((2 + 2) * 3) / 4) - 5"

Once I have this formula, I want to evaluate it and get the result: -2.

MathLib
<URL:http://www.palmbytes.de/content/dotnet/mathlib.htm>