Is there a variable, that can hold letters and decimals c++? - c++

Question

I am making a program, that can calculate a triangle if given some information but if I try to use "letters" or "," then, the program glitches and the program needs to be restarted. I am currently using double to hold the numbers and decimals but one of the rules with double is that you need to use "." for decimals, but i've hit the "," so much so I want to know if there is a way to fix it. I also want to know if the person can choose to write both numbers and letters in the same box.
#include <iostream>
#include <windows.h>
#include <math.h>
#define PI 3.14159265359
using namespace std;
void SetColor(int ForgC);
int failure = 0;
int wait;
double a, b, c, A, B, C = 90;
int main()
{
SetColor(10);
{
info:
while (GetAsyncKeyState(VK_RETURN))
{
}
system("cls");
cout << "\n\t\t\t\tFind triangle info\n" << endl;
SetColor(11);
cout << "\t\t\t\tNote: Use 0 if you don't have the number!" << endl;
SetColor(10);
cout << "What information do you have?";
SetColor(11);
cout << "\tIf you use decimal numbers then use \".\" not \",\"!";
SetColor(10);
cout << "a = ";
cin >> a;
cout << "b = ";
cin >> b;
cout << "c = ";
cin >> c;
cout << "A = ";
cin >> A;
cout << "B = ";
cin >> B;
while (GetAsyncKeyState(VK_RETURN))
{
}
}
{
calculate:
if (a == 0 && b == 0 && c == 0 && A == 0 && B == 0)
{
cout << "There need to be at least two numbers!\n" << endl;
system("pause");
failure = 1;
} // Failsafe
else if (c != 0)
{
if (a >= c || b >= c)
{
cout << "a or b cannot be greater than c!\n" << endl;
system("pause");
failure = 1;
}
} // Failsafe 2
else if (A >= 90 || B >= 90)
{
cout << "A or B cannot be equal to, or greater than 90!\n" << endl;
system("pause");
failure = 1;
;
} // Failsafe 3
if (a != 0 && c != 0)
{
b = sqrt(c * c - a * a);
A = asin(a / c) * 180 / PI;
B = 90 - A;
}
else if (b != 0 && c != 0)
{
a = sqrt(c * c - b * b);
A = acos(b / c) * 180 / PI;
B = 90 - A;
}
else if (a != 0 && b != 0)
{
c = sqrt(a * a + b * b);
A = atan(a / b) * 180 / PI;
B = 90 - A;
}
else if (c != 0 && A != 0)
{
a = c * sin(A);
b = c * cos(A);
B = 90 - A;
}
else if (c != 0 && B != 0)
{
A = 90 - B;
a = c * sin(A);
b = c * cos(A);
}
else if (a != 0 && B != 0)
{
b = a * tan(B);
c = sqrt(a * a + b * b);
A = 90 - B;
}
else if (b != 0 && A != 0)
{
a = b * tan(A);
c = sqrt(a * a + b * b);
B = 90 - A;
}
else if (a != 0 && A != 0)
{
b = a / tan(A);
c = sqrt(a * a + b * b);
B = 90 - A;
}
else if (b != 0 && B != 0)
{
a = b / tan(B);
c = sqrt(a * a + b * b);
A = 90 - B;
}
if (failure == 1)
{
goto failsafe;
}
goto answer;
}
{
failsafe:
failure = 0;
system("cls");
cout << "\n\t\t\t\tFind triangle info\n" << endl;
SetColor(11);
cout << "\t\t\t\tNote: Use 0 if you don't have the number!" << endl;
SetColor(10);
cout << "What information do you have?";
SetColor(11);
cout << "\tIf you use decimal numbers then use \".\" not \",\"!";
SetColor(10);
cout << "a = ";
cin >> a;
cout << "b = ";
cin >> b;
cout << "c = ";
cin >> c;
cout << "A = ";
cin >> A;
cout << "B = ";
cin >> B;
while (GetAsyncKeyState(VK_RETURN))
{
}
goto calculate;
}
answer:
while (1)
{
system("cls");
wait = 1;
cout << "\n\t\t\t\tFind triangle info\n" << endl;
SetColor(11);
cout << "\t\t\t\tNote: Use 0 if you don't have the number!" << endl;
SetColor(10);
cout << "What information do you have?";
SetColor(11);
cout << "\tIf you use decimal numbers then use \".\" not \",\"!";
SetColor(10);
cout << "a = " << a << endl;
cout << "b = " << b << endl;
cout << "c = " << c << endl;
cout << "A = " << A << endl;
cout << "B = " << B << endl;
cout << "C = " << C << endl;
cout << "\nDo you want to write new information? (";
SetColor(9);
cout << "Y";
SetColor(10);
cout << "/N)";
while (wait == 1)
{
if (GetAsyncKeyState(VK_RIGHT))
{
wait = 0;
}
else if (GetAsyncKeyState(VK_RETURN))
{
goto info;
}
}
system("cls");
wait = 1;
cout << "\n\t\t\t\tFind triangle info\n" << endl;
SetColor(11);
cout << "\t\t\t\tNote: Use 0 if you don't have the number!" << endl;
SetColor(10);
cout << "What information do you have?";
SetColor(11);
cout << "\tIf you use decimal numbers then use \".\" not \",\"!";
SetColor(10);
cout << "a = " << a << endl;
cout << "b = " << b << endl;
cout << "c = " << c << endl;
cout << "A = " << A << endl;
cout << "B = " << B << endl;
cout << "C = " << C << endl;
cout << "\nDo you want to write new information? (Y/";
SetColor(9);
cout << "N";
SetColor(10);
cout << ")";
while (wait == 1)
{
if (GetAsyncKeyState(VK_LEFT))
{
wait = 0;
}
else if (GetAsyncKeyState(VK_RETURN))
{
return 0;
}
}
}
}
void SetColor(int ForgC)
{
WORD wColor;
// We will need this handle to get the current background attribute
HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
CONSOLE_SCREEN_BUFFER_INFO csbi;
// We use csbi for the wAttributes word.
if (GetConsoleScreenBufferInfo(hStdOut, &csbi))
{
// Mask out all but the background attribute, and add in the forgournd color
wColor = (csbi.wAttributes & 0xF0) + (ForgC & 0x0F);
SetConsoleTextAttribute(hStdOut, wColor);
}
return;
}

Answer 1

You need to add error handling.
If input fails, you need to decide what to do. E.g. you can print an error message, clear the stream state and start over:
std::cin.exceptions(std::ios::failbit);
try
{
std::cout << "a = ";
std::cin >> a;
std::cout << "b = ";
std::cin >> b;
std::cout << "c = ";
std::cin >> c;
std::cout << "A = ";
std::cin >> A;
std::cout << "B = ";
std::cin >> B;
} catch(std::exception const& e)
{
std::cerr << "Error in input.\n";
std::cin.clear();
std::cin.ignore(std::numeric_limits<std::streamsize>::max());
goto info;
}
May I heartily suggest not using goto for program flow (use loops). And you may also use non-exception error checking:
std::cout << "a b c A B = ";
if (!(std::cin >> a >> b >> c >> A >> B))
{
if (std::cin.eof())
{
std::cerr << "Goodbye\n";
exit(1);
}
std::cerr << "Error in input.\n";
std::cin.clear();
std::cin.ignore(std::numeric_limits<std::streamsize>::max());
goto info;
}
PS. For the numeric_limits traits, include
#include <limits>

Answer 2

Apart from the usual tricky error handling with text input, in particular on the console, and the funny gotos: In order to change number formats (and others as well) you probably need to "imbue a locale" on cin (and, for consistency, on cout). I have never done it but this site has examples which look reasonable and simple: http://www.linuxtopia.org/online_books/programming_books/c++_practical_programming/c++_practical_programming_101.html