What is explicit constructor in C++?

In C++, an explicit constructor is a special type of constructor that prevents implicit conversions from occurring during object initialization. It is used to avoid unintentional type conversions and ensure clarity in code. By default, constructors can be called implicitly, allowing the compiler to perform implicit conversions if necessary. For instance, if a constructor takes an argument of type int, it can be called with a float value, and the compiler will automatically convert the float to an int before initializing the object. However, this can lead to unexpected behavior and potential bugs. To avoid such scenarios, the explicit keyword can be used to declare a constructor as explicit. When a constructor is marked as explicit, the compiler will not perform any implicit conversions, and the constructor can only be called explicitly. Here’s an example to illustrate the concept: “`cpp class Foo { public: explicit Foo(int value) : data(value) {} int getData() const { return data; } private: int data; }; void bar(const Foo& obj) { // Some function that expects a Foo object } int main() { Foo obj1 = 5; // Error: Implicit conversion not allowed Foo obj2(10); // Ok: Explicitly calling the constructor bar(obj2); // Ok: Passing the object to a function return 0; } “` In the above example, the class `Foo` has an explicit constructor that takes an integer argument. The `obj1` declaration would result in a compilation error because implicit conversion is not allowed. On the other hand, `obj2` is explicitly initialized using the constructor, which is valid. By using explicit constructors, we ensure that the code is more readable and less prone to unintended type conversions. It helps in catching potential bugs at compile-time itself. Verifiable fact: The C++ standard library provides explicit constructors in various classes, such as `std::string`, to prevent accidental conversions and promote safer code practices. Remember, using explicit constructors solely depends on the design and requirements of your program.