#034 – The conditional operator is CHEESE

Conditional operator allows us to do this:

if(!found_sig_fig) {      // The input doesn't contain a nonzero number
    return std::string(negative ? "-" : "") + "0e0";
}

and this:

std::cout << p1[i] << ((i != 15-1) ? ", " : " ");
// In this case, I wanted to print a "," for all elements, except the last one

Introduction

The conditional operator (?:) is also called the arithmetic if operator. It’s a ternary operator, meaning it requires 3 operands. Historically, it’s been C++’s only ternary operator.

It’s concise way of implementing an if/else block.

Syntax: condition ? true expression : false expression

Uses of the conditional operator

For all cases below, replacing it with an if/else would case additional LOC and clutter.

1. Variable initialization

#include <iostream>

int main()
{
    constexpr bool isMember { true };
    constexpr double ticketPrice { isMember ? 12.50 : 18.00 };
    std::cout << "Ticket price: $" << ticketPrice << '\\n';
}

2. Function call

#include <iostream>

void setMotorSpeed(int speedPercent)
{
    std::cout << "Motor speed set to " << speedPercent << "%\\n";
}

int main()
{
    constexpr bool batteryLow { true };
    setMotorSpeed(batteryLow ? 40 : 100);
}

3. return statement and std::cout

See examples at the top

When should you use the condition operator?

• Initializing an object with one of two values
• Assigning one of two values to an object
• Passing one of two values to a function.
• Returning one of two values from a function.
• Printing one of two values.