检测输入值是否为整型

#include <iostream>
#include <climits>
#include <string>
#include <math.h>
#define _CRT_SECURE_NO_WARNINGS

bool is_num(char*); //Check whether the input only consists of number or not
bool test_limits(double); //Check whether the input falls within the C++ integer limits

int main()
{
    using namespace std;

    //Get the initial input
    cout << "Yo, dude! Enter an integer value:\n";
    char str[999];
    cin >> str;

    //Set an indicator
    bool pass = false;

    //Create a pointer points to the addresss of the first character of the input
    char *num;

    //Create a double variation for the bound test
    double numberForTest = 0;

    //Valuation
    while (!pass)
    {
        num = str;

        //Check Round 1
        if (!is_num(num))
        {
            cout << "Please enter an integer\n";
            cin >> str;
        }

        //Check round 2
        else
        {
            //Get the double form of the input 
            for (int temp = strlen(str) - 1; *num; num++, temp--)
            {
                numberForTest += (int(*num) - 48)*pow(10, temp);
            }

            if (!test_limits(numberForTest))
            {
                cout << "Out of range -- please try again:\n";
                numberForTest = 0;
                cin >> str;
            }
            else
                pass = true;
        }
    }

    cout << "You have entered the integer " << numberForTest << "\nBye\b";
    return 0;
}

bool is_num(char *x)
{
    for (; *x; x++)
    {
        if ('0' <= *x&&*x <= '9')
            continue;
        else
            return false;
    }
    return true;
}

bool test_limits(double a)
{
    if (INT_MIN <= a && a <= INT_MAX)
        return true;
    else
        return false;
}