/*Example to demonstrate functions. We're going to use the predefined functions
 * in the math library (cmath) and the standard library (cstdlib).
 * In order to use functions in a library, include the library
 */
#include<iostream>
#include<cmath>
#include<cstdlib>
using namespace std;

/*user defined function. Root of a quadratic equation
 * (-b +/- sqrt(b^2 - 4ac)) /2a
 * If the user picks 'P', we print the "larger" root. Otherwise, we print the other root.
 */
double quadRoot( double a, double b, double c, char pick)
{
	if(pick == 'P' || pick =='p')
		return (-b + sqrt ( b*b - 4*a*c) ) / (2*a);

	else
		return (-b - sqrt ( b*b - 4*a*c) ) / (2*a);

	//We can also store the result in a variable and return the variable
}

int main()
{
	//find the square root of a number
	cout<<"Enter a number: ";
	double num;
	cin>>num;

	double ans = sqrt(num);

	cout<<"The square root is "<<ans<<endl;
	
	sqrt(45.5); //Here, the result is returned. But we're not printing or string the result.
	//So it vanishes in mid air
	cout<<"The square root of 10 is "<<sqrt(10)<<endl;
	//We can pass literals or variables of compatible types as parameters.

	int x,y;
	cout<<"Enter x: ";
	cin>>x;
	cout<<"Enter the exponent: ";
	cin>>y;
	//functions can have multiple parameters
	cout<<"x^y is "<<pow(x,y)<<endl;

	//atof converts a number in string form to the double
	num = atof("365894.5567");
	// same as num = 365894.5567;

	cout<<sqrt(num)<<endl;

	//We can nest function calls. The inner function call is evaluated first
	cout<<"square root of a random number: "<<sqrt(rand())<<endl;
	
	int a,b,c;
	cout<<"Enter the coefficients of the quadratic equation: ";
	cin>>a>>b>>c;
	//We're using the function we defined earlier
	cout<<"The root is "<<quadRoot(a,b,c,'n')<<endl;

	return 0;
}