// Think CS ch. 4 examples
#include <iostream>
#include <cmath>
#include <ctime>
using namespace std;

void printLogarithm (double x) {
    if (x <= 0.0) {
        cout << "Positive numbers only, please." << endl;
        return;
    }

    double result = log (x);
    cout << "The log of " << x << " is " << result << endl;
}

void countdown (int n) { // n>0 please!
    if (n<0) {
        cout << " n>=0 please\n";
        return;
    }
    if (n == 0) {
        cout << "Blastoff!" << endl;
    } else {
        cout << n << endl;
        countdown (n-1);
        cout << "Backing out level " << n << endl;
    }
}

int fac (int n) {
    int recurse, result;
    cout << "Computing fac(" << n << ")...\n";
    if (n == 0) {
        result = 1;
    } else {
        recurse = fac (n-1);
        result = n * recurse;
    }
    cout << "fac(" << n << ") = " << result << endl;
    return result;

}

/*
int fac (int n) {
    if (n==0) {
        return 1;
    } else {
        return n * fac(n-1);
    }
}
*/

int main () {
//    cout << "6! = " << fac (6) << endl;
	/*
    srand(time(NULL));
    for (int i = 1; i <= 5; i++)
    	cout << (double) rand() / RAND_MAX << endl;
    return 0;
    */
	int X = 0;
	if (X = 0) {
		cout << "It's zero\n";
	} else {
		cout << "It's not zero\n";
	}
	countdown (5);
}