Math parser conversion to c++ from c

[Ivanlul]

Hello, today I found a great mathematical expression parser at http://www.yann-ollivier.org/mathlib/mathexpr.php
But there is a problem, it is written in C. I know C can be used in C++ but I do not understand the code in C. I'm wondering if there is a program that can convert c to c++ or if anyone would be willing to do it?
The total amount of code that needs to be converted is about 1400 lines so changing it by hand might be tough.

[Galik]

There is a c++ version along with the c version in the archive that you download from that site.

[Galik]

In fact it all seems to be c++, it just doesn't use the c++ standard libs. I doubt if you will find a converter for that.

[Ivanlul]

Oh okay, well I need help understanding this program, lines 22-29 and how I could change it to do something else:

#include <stdio.h>
#include "mathexpr.h"
#include <iostream>

using namespace std;
int main()
{

 // The number that the variable "x" will point to
double x;
 // Creates a variable named "x" and which value will be x
 RVar xvar ( "x" , &x );

 // Asks for a fomula depending on the variable x, e.g. "sin 2x"
 char s[500]="";
cout << "Enter a formula depending on the variable x:\n";
gets(s);

 // Creates an operation with this formula. The operation depends on one
 // variable, which is xvar; the third argument is an array of pointers
 // to variables; the previous argument is its size
 RVar* vararray[1]; vararray[0]=&xvar;
 ROperation op ( s, 1, vararray );

 // Affects (indirectly) a value to xvar
 x=3;
 // Printfs the value of the formula for x=3;
 printf("%s = %G for x=3\n\n", op.Expr(), op.Val() );
 cin.get();

 return 0;
}

[Galik]

Here is what I *think* is going on:

double x; // this is your variable for your equation. 

RVar xvar ( "x" , &x ); // RVar seems to be keeping a reference to your variable for the engine

// vararray seems to be an array of variables to be operated on 
RVar* vararray[1]; 

// In this example kust one variable is being put in the array
vararray[0]=&xvar;

// The list of variables is now being sent to the expression processing engine.
// The s is a string expression in x such as "x^2-x*4+2"
ROperation op ( s, 1, vararray );

// No the op object can be queried for the input expression(op.Expr())
and the output value (op.Val()) that will depend on the input value of x

x=3;
printf("%s = %G for x=3\n\n", op.Expr(), op.Val() );

// the printf() statement is the equivalent of this:

std::cout << op.Expr() << " = " << op.Val() << " for x=" << x << "\n\n";