Convert a string mathematic expression to float

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Hello how can i convert a string mathematic expression to float.
Here is an example:

"((23.5*2)+(45+0.4)-1.3)"
function should return: 91.1

Thank you

Posted 8-Mar-14 2:25am

Dionisios Karatzas

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4 solutions

Solution 1

You have to know that C++ is a compiled language. Therefore, at runtime you cannot easily interpret a language expression. What you need to employ is a library (or your own code) that interprets and evaluates the expression.

Look for example here: http://fastmathparser.codeplex.com/[^]

or here: http://muparser.beltoforion.de/[^]

Posted 8-Mar-14 2:32am

nv3

Solution 3

.NET Rational (fraction) value type using Decimals, written in C#[^]

PIEBALD.Types.Rational g = 
   PIEBALD.Types.Rational.ParseInfix ( "((23.5*2)+(45+0.4)-1.3)" ) ;

float x = (float) g ;

Posted 8-Mar-14 3:03am

PIEBALDconsult

Solution 4

I know this has already been answered, but maybe as a complement, youm ay check toxcct's article which embeds a parser:
Visual Calc v3.0 - A new dimension for the desktop calculator[^]

Posted 10-Mar-14 3:13am

Rage

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OriginalGriff · Accepted Answer · 2014-03-08T02:33:00

Solution 2

You need an evaluator. Have a look here: Expression evaluator : using RPN[^]

Posted 8-Mar-14 2:33am

OriginalGriff