calculator troubles

[ascii]

im making a calculator to which you should be able to input something like:
12+54 and get 66. im working only with addition and two numbers right now and am having trouble. right now its adding the digits of the numbers then adding them together. i dont understand how i can make it so that it makes the number first, and then converts it to an int value which is added to the total. please please please help :)
you dont really need to go through the code for this i just need ideas. here it is anyhow

#include<iostream>
using std::cout;
using std::endl;
using std::cin;
char* eatspaces(char* str, int length, char* expression);
int addNumbers(char* str, int length, int num1, int num2);
int findLength(char* str, int length);

int main(void)
{
	const int max = 50;
	char equation[max];
	char* pequation = equation;
	cout << "Equation: " << endl;
	cin.getline(equation, 15, '\n');
	
	int length = 0;
	for (int i = 0; equation[i] != '\0'; i++)
		length++;
	char* expression = new char[length];
	expression = eatspaces(equation, length, expression);
	int num1Length = findLength(expression, length);
	int num2Length = num1Length + 2;
	int total = addNumbers(expression, length, num1Length, num2Length);

	cout << "total is: " << total << endl;

	delete[] expression;
	expression = NULL;
	pequation = NULL;
	return 0;
}

char* eatspaces(char* str, int length, char* expression)
{
	int spaceCounter = 0;
	for (int i = 0; i < length; i++)
	{
		if (str[i] == ' ')
			continue;
		else
			expression[spaceCounter] = str[i];
			spaceCounter++;
	}
	return expression;
}

int findLength(char* str, int length)
{
	int num1Length = 0;
	for (int i = 0; str[i] != '+'; i++)
		num1Length++;
	return num1Length;
}

int addNumbers(char* str, int length, int num1, int num2)
{
	int total = 0;		
	for (int i = 0; i < num1; i++)
		total += (str[i] - 48);
	num1++;
	for (; num1 < length; num1++)
		total += (str[num1] - 48);
	
	return total;
}

[D80DSL3A]

One way is to use a stringstream object. Here is a sample code which works:

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

int main()
{
	char exp[] = "12+54";// char array after spaces have been "eaten"
	stringstream ss(exp);// initialize stream with exp[]
	int x=0, y=0;// variables to stream exp into
	char oper='-';
	ss >> x >> oper >> y;// stream the values in

        // display contents of variables and find the total
	cout << "x = " << x << ", oper = " << oper << ", y = " << y << endl;
	cout << "Total = " << x+y << endl;
	return 0;
}

[ascii]

possibly but i feel like my prof would have taught us that before the assignment :o

[TheNoobie]

I can't imagine your professor getting mad at you for using programming that he hasn't even taught yet unless he explicitly told you what you can and can not use.