制作二次根项目，我的第二组嵌套的“IF”语句被忽略

Question

To quickly explain, I need six different possible cout outputs. Three for when A = 0 which don't work, and then three more for when it doesn't equal 0 which work flawlessly. I think I know my problem, the set of if statements under '//A DOES equal 0', can never run. What's wrong with my second set of nested if statements?

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

int main() {
    double numA = 0;
    double numB = 0;
    double numC = 0;
    int rootOne = 0;
    int rootTwo = 0;

    // User inputs roots

    cout << "Program computes and prints the real roots of a quadratic polynomial a*x^2 + b*x + c." << endl;
    cout << "Enter three real numbers a, b, c, seperated by spaces:";
    cin >> numA >> numB >> numC;

    //Calculating the Roots; (-b + sqrt(b * b - 4 * a * c)) / (2 *a) and (-b - sqrt(b * b - 4 * a * c)) / (2 *a)
    rootOne = (-numB + sqrt(numB * numB - 4 * numA * numC)) / (2 * numA);
    rootTwo = (-numB - sqrt(numB * numB - 4 * numA * numC)) / (2 * numA);

    // A doesn't equal 0
    if (numA != 0) {
        if ((numB * numB) - (4 * numA * numC) > 0) {
            cout << "The quadratic polynomial " << numA << "*x^2 + " << numB << "*x + " << numC << " has two distinct real roots" << endl;
            cout << "root 1 = " << rootOne << " root2 = " << rootTwo << endl;

        } else if ((numB * numB) - (4 * numA * numC) == 0) {
            cout << "The quadratic polynomial " << numA << "*x^2 + " << numB << "*x + " << numC << " has two equal real roots" << endl;
            cout << "root 1 = root2 = " << rootTwo << endl;

        } else if ((numB * numB) - (4 * numA * numC) < 0) {
            cout << "The quadratic polynomial " << numA << "*x^2 + " << numB << "*x + " << numC << " has two complex roots" << endl;
        }
    }

    //A does equal 0
    if (numA == 0) {
        if ((numB == 0) && (numC != 0)) {
            cout << "No roots for the constand function of " << numC << endl;
        } else if ((numB == 0) && (numC == 0)) {
            cout << "No roots for the degenerate case of 0 = 0." << endl;
        } else {
            cout << "The only root for the linear case of " << numA << "*x^2 + " << numB << "*x + " << numC << "is: " << numB << endl;
        }
    }

    return 0;
}

Answer 1

Whoops:

if (numA =! 0) {

Here you're setting numA , to !0 (which is true , then converted to 1 for the assignment).

It's the same as:

if (numA = !0) {

So it's no surprise that your subsequent if statement is "being ignored": the condition no longer matches.

If you'd turned your compiler warnings on, you'd have received a message like:

warning: suggest parentheses around assignment used as truth value

…and then you wouldn't have to guess what's going on ask us to fix your code for you.

The "not equal to" operator is != , not =! .

Answer 2

Okay, so I guess thanks for trying to help...and then insulting me, I never did learn if I nested my statements right or not but whatever. I ended up just rewriting my first nested statements and used Logical Operators like I did at the bottom. So my new code just has all six in one big nest and it worked!

The "not equal to" operator is !=, not =!

I actually thought I was doing it right before I came here so I did learn something anyway so thanks to that person, as such, you win the best answer!