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// Quadratic equation calculator.
#include <iostream>
#include <string>
#include <sstream>
#include <cmath>
double discriminant_function( double func1a, double func1b, double func1c );
double quadratic_formulaplus( double FormulaDiscriminant1, double func2a, double func2b );
double quadratic_formulaminus( double FormulaDiscriminant2, double func3a, double func3b );
int main()
{
std::string use_again;
std::string a_var_s;
double a_var = 0;
std::string b_var_s;
double b_var = 0;
std::string c_var_s;
double c_var = 0;
double discriminant = 0;
double result1 = 0;
double result2 = 0;
std::string correct_equation;
std::string correct_equation_validation;
do
{
std::cout << "\n";
std::cout << "Quadratic equation calculator, 2.0.\n";
std::cout << "\n";
std::cout << "This program only calculates quadratic equations that are in ax^2 + bx + c = 0 form.\n";
std::cout << "\n";
std::cout << "This form is also known as standard form.\n";
std::cout << "\n";
while ( correct_equation != "y" )
{
std::cout << "Input the value of a:\n";
std::getline ( std::cin, a_var_s );
std::stringstream( a_var_s ) >> a_var;
std::cout << "Input the value of b:\n";
std::getline ( std::cin, b_var_s );
std::stringstream( b_var_s ) >> b_var;
std::cout << "Input the value of c:\n";
std::getline ( std::cin, c_var_s );
std::stringstream( c_var_s ) >> c_var;
std::cout << "\n";
std::cout << "Did you mean to input the following equation: " << a_var << "x^2";
if ( b_var >= 0 )
std::cout << "+" << b_var << "x";
else
std::cout << b_var << "x";
if ( c_var >= 0 )
std::cout << "+" << c_var;
else
std::cout << c_var;
std::cout << " = 0?\n";
std::cout << "\n";
do
{
std::cout << "Input 'y' if the equation was correct.\n";
std::cout << "Input 'n' if the equation was incorrect.\n";
std::cin >> correct_equation;
if ( correct_equation != "y" && correct_equation != "n" )
{
correct_equation_validation = "n";
std::cout << "Invalid user input. Please try again.\n";
std::cout << "\n";
}
else if ( correct_equation == "y" )
correct_equation_validation = "y";
else
{
correct_equation_validation = "y";
correct_equation = "n";
}
}
while ( correct_equation_validation == "n" );
}
discriminant = discriminant_function( a_var, b_var, c_var );
std::cout << "The discriminant of the equation is " << discriminant << ".\n";
std::cout << "Therefore: ";
if ( discriminant >-0.00000000001 && discriminant < 0.00000000001 ) // Never use == to compare floating point variables.
{
std::cout << "x can only have one real value.\n";
result1 = quadratic_formulaplus( discriminant, a_var, b_var );
std::cout << "x = " << result1;
}
else if ( discriminant < 0 )
{
std::cout << "x has no real values.\n";
}
else
{
std::cout << "x has two real values.\n";
result1 = quadratic_formulaplus( discriminant, a_var, b_var );
std::cout << "x = " << result1 << "\n";
result2 = quadratic_formulaminus( discriminant, a_var, b_var );
std::cout << "OR: x = " << result2 << "\n";
}
std::cout << "Input 'y' to use this program again:\n";
std::cin >> use_again;
std::cin.ignore();
a_var_s.clear();
b_var_s.clear();
c_var_s.clear();
a_var = 0;
b_var = 0;
c_var = 0;
result1 = 0;
result2 = 0;
correct_equation.clear();
correct_equation_validation.clear();
}
while ( use_again == "y" );
return 0;
}
double discriminant_function( double func1a, double func1b, double func1c )
{
return func1b * func1b - 4 * func1a * func1c;
}
double quadratic_formulaplus( double FormulaDiscriminant1, double func2a, double func2b )
{
double root_var1 = 0;
root_var1 = sqrt( FormulaDiscriminant1 );
double dividend1 = 0;
dividend1 = -1 * func2b + root_var1;
double divisor1 = 0;
divisor1 = 2 * func2a;
double res1 = 0;
res1 = dividend1/divisor1;
return res1;
}
double quadratic_formulaminus( double FormulaDiscriminant2, double func3a, double func3b )
{
double root_var2 = 0;
root_var2 = sqrt( FormulaDiscriminant2 );
double dividend2 = 0;
dividend2 = -1 * func3b - root_var2;
double divisor2 = 0;
divisor2 = 2 * func3a;
double res2 = 0;
res2 = dividend2/divisor2;
return res2;
}
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