C++ floating point to integer type conversions

Question

What are the different techniques used to convert float type of data to integer in C++?

#include <iostream>

using namespace std;
struct database {
  int id, age;
  float salary;
};

int main() {
  struct database employee;
  employee.id = 1;
  employee.age = 23;
  employee.salary = 45678.90;
  /*
     How can i print this value as an integer
     (with out changing the salary data type in the declaration part) ?
   */
  cout << endl << employee.id << endl << employee.
  age << endl << employee.salary << endl;
  return 0;
}

Answer 1

What you are looking for is 'type casting'. typecasting (putting the type you know you want in brackets) tells the compiler you know what you are doing and are cool with it. The old way that is inherited from C is as follows.

float var_a = 9.99;
int   var_b = (int)var_a;

If you had only tried to write

int var_b = var_a;

You would have got a warning that you can't implicitly (automatically) convert a float to an int, as you lose the decimal.

This is referred to as the old way as C++ offers a superior alternative, 'static cast'; this provides a much safer way of converting from one type to another. The equivalent method would be (and the way you should do it)

float var_x = 9.99;
int   var_y = static_cast<int>(var_x);

This method may look a bit more long winded, but it provides much better handling for situations such as accidentally requesting a 'static cast' on a type that cannot be converted. For more information on the why you should be using static cast, see this question.