Evaluating arithmetic expressions using recursive descent parser

[johnsmith2]

I have the following code to calculate arithmetic expressions :

#include <iostream>
using namespace std;

using namespace std;

const char * expressionToParse = "6.5-2.5*10/5+2*5";

char peek()
{
    return *expressionToParse;
}

char get()
{
    return *expressionToParse++;
}

double expression();

double number()
{
    double result = get() - '0';
    while (peek() >= '0' && peek() <= '9')
    {
        result = 10*result + get() - '0';
    }
    return result;
}

double factor()
{
    if (peek() >= '0' && peek() <= '9')
        return number();
    else if (peek() == '(')
    {
        get(); // '('
        double result = expression();
        get(); // ')'
        return result;
    }
    else if (peek() == '-')
    {
        get();
        return -expression();
    }
    return 0; // error
}

double term()
{
    double result = factor();
    while (peek() == '*' || peek() == '/')
        if (get() == '*')
            result *= factor();
        else
            result /= factor();
    return result;
}

double expression()
{
    double result = term();
    while (peek() == '+' || peek() == '-')
        if (get() == '+')
            result += term();
        else
            result -= term();
    return result;
}

int main(double argc, char* argv[])
{

    double result = expression();
	cout << result << endl;
    return 0;
}

The problem is that it does not work properly with decimal numbers
for example it evaluates 6-2*10/5+2*5 = 12 which is correct but for 6.5-2.5*10/5+2*5 it returns 6 instead of 11.5 .
can someone please help me to fix this issue ?

[cire]

number doesn't handle decimal points (and if it did factor doesn't.)

[johnsmith2]

is there anyway to modify it to handle decimals ? I am not really sure what to do

[cire]

#include <sstream>
#include <iostream>
using namespace std;

const char * expressionToParse = "6.5-2.5*10/5+2*5";

istringstream parse(expressionToParse) ;

char peek()
{
    return static_cast<char>(parse.peek()) ;
}

char get()
{
    return static_cast<char>(parse.get()) ;                    
}

double expression();

double number()
{
    double result ;
    parse >> result ;                      
    return result;
}

double factor()
{
    if ((peek() >= '0' && peek() <= '9') || peek() == '.')
        return number();
    // rest of the code doesn't require change...