#include <iostream>
#include <cmath>
#include <string>
/*
============================================================
Convert a decimal-like value to a long in C++.
This program demonstrates:
• Conversion using std::lround(), which rounds to nearest.
• Conversion using static_cast<long>(), which truncates.
• A helper function that prints both results.
Notes:
• C++ does not have a built-in decimal type.
• double or long double are used for decimal values.
• std::lround() follows IEEE rounding rules.
• static_cast<long>() truncates toward zero.
============================================================
*/
class DecimalToLongProgram {
public:
// Converts a floating decimal value to long using rounding.
static long ConvertDecimalToLong(double value) {
return std::lround(value);
}
// Converts a floating decimal value to long using truncation.
static long CastDecimalToLong(double value) {
return static_cast<long>(value);
}
// Prints both conversion styles for comparison.
static void ShowConversions(double value) {
std::cout << "Input decimal: " << value << "\n";
long rounded = ConvertDecimalToLong(value);
long truncated = CastDecimalToLong(value);
std::cout << "Rounded (std::lround): " << rounded << "\n";
std::cout << "Truncated (static_cast<long>): " << truncated << "\n\n";
}
};
int main() {
// Example values to demonstrate behavior
DecimalToLongProgram::ShowConversions(12.7);
DecimalToLongProgram::ShowConversions(12.3);
DecimalToLongProgram::ShowConversions(-5.8);
DecimalToLongProgram::ShowConversions(42.0); // already an integer
}
/*
run:
Input decimal: 12.7
Rounded (std::lround): 13
Truncated (static_cast<long>): 12
Input decimal: 12.3
Rounded (std::lround): 12
Truncated (static_cast<long>): 12
Input decimal: -5.8
Rounded (std::lround): -6
Truncated (static_cast<long>): -5
Input decimal: 42
Rounded (std::lround): 42
Truncated (static_cast<long>): 42
*/
