Mathematical input parser

I made a simple math expressions solver that using a "for" loop iterates over all the characters and stores the numbers and signs in std::vector.
It give support for unlimited parentheses and does multiplications and division before other calculations.
I really appreciate if you give any suggestions.
Here's the code:

using std::cout;
using std::endl;
using std::cin;
using std::vector;
using std::string;

void input(vector &, vector &, vector &, vector &, string);

int numLenght(int index, string poly)
{
    int lenght = 0;
    for (int i = index; i  num, vector sign)
{
    float result = 0;
    for (unsigned i = 0; i  &num, vector &sign, vector &firstPos, vector minus)
{
    for (unsigned i = 0; i  &num)
{
    double tempNum = 0;
    string parOp;
    vector num1;
    vector sign1;
    vector firstPos1;
    vector minus1;
    i += 2;
    for (int j = i; j  &sign, string poly, int &i, vector &firstPos, vector &minus)
{
    char next = poly[i + 1];
    if (!(i == poly.length() - 1))
    {
        sign.push_back(next);
        int posTemp = sign.size() - 1;
        if (next == '*' || next == '/')
        {
            firstPos.push_back(posTemp);
        }
        if (poly[i + 2] == '-')
        {
            int posMinus = sign.size() - 1;
            minus.push_back(posMinus);
            i++;
        }
        i++;
    }
}

void input(vector &num, vector &sign, vector &firstPos, vector &minus, string poly)
{
    for (int i = 0; i  num;
    vector sign;
    vector firstPos;
    vector minus;
    string poly;
    cout > poly;
    input(num, sign, firstPos, minus, poly);
    for (int i = 0; i > choose;
    if (choose == 's')
        main();
    return 0;
}

Think more about the logic

Right now, your numlenght also has some logic that doesn't seem to me like it makes much sense at all:

if (i == poly.length() - 1)
    {
        break;
    }
    else
    {
        break;
    }

It appears that the test in the if statement makes no real difference at all--you're going to carry out the same action whether it's true or false. You might as well replace that whole chunk with break; (but before you edit, see the next point below).

Use the standard library

Your numLenght [sic] could be implemented a lot more easily using find_first_not_of:

return poly.find_first_not_of("0123456789");

Names

At least to me, some of you names seem fairly meaningless. For example, I'm not sure what parHandler is supposed to mean.

Conclusion

Ultimately, I agree with Loki Astari this this would be much better handled with a recognizable lexer and parser. Rather than post some code for that, I'll point you to a previous question where both he and I posted our ideas of how to accomplish roughly what you're doing here.

StackExchange Code Review Q#133042, answer score: 2