We have discussed that there are some techniques to manipulate a function. We will gain many advantages from it. Since we can implement the first-class function in the C++ language, we can pass a function as another function's parameter. We can treat a function as a data object so we can assign it to a variable and store it in the container. Also, we can compose a new function from the existing one. Moreover, by using map, filter, and fold, we can implement the higher-order function in every function we create.
Another technique we have to implement in gaining a better functional code is a pure function to avoid a side effect. We can refactor all the functions we have so it won't talk to outside variables or states and won't change and retrieve the value from the outside state. Also, to reduce the multiple arguments function so we can evaluate its sequence...
