In C++, stack literals are a convenient way to initialize and use a stack data structure. However, C++ does not provide built-in support for creating custom stack literals. In this blog post, we will explore how to create custom stack literals in C++ using user-defined literals.

User-Defined Literals

User-defined literals are a feature introduced in C++11 that allow you to define your own syntax for literal values of various types. These literals are defined by appending a suffix to a numeric or string literal. For example, you can define a custom literal for creating a distance object like this:

class Distance {
public:
  Distance(long double meters) : meters(meters) {}
  
private:
  long double meters;
};

constexpr Distance operator"" _m(long double meters) {
  return Distance(meters);
}

In the code above, we define a user-defined literal _m that converts a long double literal to a Distance object. Now we can create distance objects using this literal like this:

auto d = 5.5_m; // creates a Distance object representing 5.5 meters

Implementing Custom Stack Literals

To implement custom stack literals, we can follow a similar approach. First, we need to define a stack class:

#include <vector>

template <typename T>
class Stack {
public:
  void push(const T& value) {
    data.push_back(value);
  }
  
  T pop() {
    T value = data.back();
    data.pop_back();
    return value;
  }
  
private:
  std::vector<T> data;
};

Now, let’s define a user-defined literal _s that converts a string literal to a stack object:

constexpr Stack<char> operator"" _s(const char* str, size_t size) {
  Stack<char> stack;
  for (size_t i = 0; i < size; ++i) {
    stack.push(str[i]);
  }
  return stack;
}

In the code above, we define a user-defined literal _s that takes a string literal and converts it into a Stack<char> object. Each character in the string literal is pushed onto the stack.

We can now use this custom stack literal to create stack objects like this:

auto s = "Hello"_s; // creates a Stack<char> object with 'H', 'e', 'l', 'l', 'o' in it

Conclusion

Creating custom stack literals in C++ allows us to write more expressive and concise code when working with stacks. By leveraging user-defined literals, we can define our own syntax for creating various types of stack objects. This provides a more intuitive and flexible way to work with stacks in C++.