string formula to real formula

Question

Hi,

I'd like to convert a string to a variable formula in C#. I mean that I wanna write as the following.


string formula="a*b";
int a;
int b;
int ans= formula //here I want to convet formula to.........

Is there any way to solve my problem? Please help me.

REgard.

Answer 1

 You can convert integer which are represented as strings to int variables using the int.Parse() method. But, Converting string "a*b" to int doesn't make any sense.

Answer 2

I think you are trying to evaluate the expressions.

Check these link

http://blog.lozanotek.com/archive/2004/12/31/180.aspx

http://www.codeproject.com/KB/recipes/matheval.aspx

---

Pradeep Sethi

Answer 3

Here is one way I wrote, using dynamic code generation and compilation. It's a bit of a sledgehammer to crack a nut though - but you might find it of interest. It's a console app:

using System;

using System.Reflection;

using System.CodeDom.Compiler;

using Microsoft.CSharp;

/// <summary>This simple program demonstrates how to dynamically compile code.</summary>

class Program

{

static void Main()

{

TestExpression("2+1-(3*2)+8/2");

TestExpression("1*2*3*4*5*6");

TestExpression("Invalid expression");

}

static void TestExpression(string expression)

{

try

{

int result = EvaluateExpression(expression);

Console.WriteLine("'" + expression + "' = " + result);

}

catch (Exception)

{

Console.WriteLine("Expression is invalid: '" + expression + "'");

}

}

public static int EvaluateExpression(string expression)

{

string code = string.Format  // Note: Use "{{" to denote a single "{"

(

"public static class Func{{ public static int func(){{ return {0};}}}}",

expression

);

CompilerResults compilerResults = CompileScript(code);

if (compilerResults.Errors.HasErrors)

{

throw new InvalidOperationException("Expression has a syntax error.");

}

Assembly assembly = compilerResults.CompiledAssembly;

MethodInfo method = assembly.GetType("Func").GetMethod("func");

return (int)method.Invoke(null, null);

}

public static CompilerResults CompileScript(string source)

{

CompilerParameters parms = new CompilerParameters();

parms.GenerateExecutable = false;

parms.GenerateInMemory = true;

parms.IncludeDebugInformation = false;

CodeDomProvider compiler = CSharpCodeProvider.CreateProvider("CSharp");

return compiler.CompileAssemblyFromSource(parms, source);

}

}

Answer 4

Is it possible to get some precision with this code? like 1+1/2 = 1.5 ?

Answer 5

Yes, change the "int" to "double" in the code, and enter numbers that contain decimal points, e.g. 1.0+1.0/2.0