Multi tool use

Clash Royale CLAN TAG

Is there a way to improve this this c++ code?

Hello

I'm a programming newbie. In fact, this is my second code ever (after the hello world code).

I did a lot of reading actually, here on stack overflow, and other websites, I also purchased "Jumping Into C++" By Alex Allain, And I put Everything I learned here In this code :

Simple Calculator.cpp :

#include <iostream>
#include <string>
using std::cout; using std::cin;

int main()
{
cout << "Calculator..... n";
cout << "Type '3a3'to exit... n";

double a=0 ,b=0;
char op = 'a'; //operator // 'a' is the exit operator, the value of the integers doesn't matter

int ch = 0; //while loop checker

do
{
cin >> a >> op >> b;
if (op == '/' && b == 0)
{
cout << "Division By Zero, Please Retry n" ;
goto retry;
}
switch (op)
{
case '+':
cout << a << " + "<< b << " = " << a+b << "n";
ch = 0 ;
break;

case '-':
cout << a << " - "<< b << " = " << a-b << "n";
ch = 0 ;
break;

case 'x':
case '*':
cout << a << " * "<< b << " = " << a*b << "n";
ch = 0 ;
break;

case '/':
cout << a << " / "<< b << " = " << a/b << "n";
ch = 0;
break;

case 'a':
ch = 1;
break;

default:
ch = 0;
cout << "Invalid operator, Please retry n";
}

retry: ;

}while (ch != 1);

}


I would Like To know If there's a way to further improve this code.

Thanks In Advance

goto

else

if (op == '/' && b == 0)

1 Answer
1

"foobar"s with std::literals::string_literals::operator""s() accessible in the global namespace constructs a std::string from "foobar".

"foobar"s

std::literals::string_literals::operator""s()

std::string

"foobar"

#include <limits>
#include <string>
#include <iostream>

using namespace std::literals::string_literals;

int main()
{
std::cout << "Calculator..... nType '3a3' to exit...n";

char op;
do
{
double lhs, rhs;
while (std::cout << "> ", // print a promt. due to the comma operator this is not part of the condition
!(std::cin >> lhs >> op >> rhs) || // input error, cin is in a error state ... !cin
"+-*x/:a"s.find(op) == std::string::npos || // op is not a valid operation
"/:"s.find(op) != std::string::npos && rhs == .0) // op is division and the divisor (right-hand-side operand) is zero
{
std::cerr << "Input error!nn";
std::cin.clear(); // clear error state of cin
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n'); // ignore everything up to a newline stille in the input buffer
}
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');

double result;
switch (op)
{
case '+':
result = lhs + rhs;
break;
case '-':
result = lhs - rhs;
break;
case '*':
case 'x':
result = lhs * rhs;
break;
case '/':
case ':':
result = lhs / rhs;
break;
}
if (op != 'a')
std::cout << lhs << ' ' << op << ' ' << rhs << " = " << result << 'n';

} while (op != 'a');
}


shorter:

#include <limits>
#include <string>
#include <iostream>
#include <functional>

using namespace std::literals::string_literals;

int main()
{
std::cout << "Calculator..... nType '3a3' to exit...n";
std::function<double(double, double)> ops{
[&](double lhs, double rhs) { return lhs + rhs; },
[&](double lhs, double rhs) { return lhs - rhs; },
[&](double lhs, double rhs) { return lhs * rhs; },
[&](double lhs, double rhs) { return lhs / rhs; } };
char op;
do
{
double lhs, rhs;
std::size_t op_pos;

while (std::cout << "> ",
!(std::cin >> lhs >> op >> rhs) ||
(op_pos = "+ - *x/:a "s.find(op)) == std::string::npos ||
"/:"s.find(op) != std::string::npos && rhs == .0)
{
std::cerr << "Input error!nn";
std::cin.clear();
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');
}
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), 'n');

if (op != 'a')
std::cout << lhs << ' ' << op << ' ' << rhs << " = " << ops[op_pos/2](lhs, rhs) << 'n';

} while (op != 'a');
}


"+-*x/:a"s

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