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Learning C++ Functional Programming
Learning C++ Functional Programming

Learning C++ Functional Programming: Explore functional C++ with concepts like currying, metaprogramming and more

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Learning C++ Functional Programming

Manipulating Functions in Functional Programming

In the previous chapter, we talked about modern C++ in depth, especially about the new feature in C++11--the Lambda expression. As we discussed earlier, the Lambda expression is useful in simplifying function notation. Thus, in this chapter, we will apply the power of the Lambda expression again, which will be used in functional code, especially when we talk about currying--the technique to split and reduce the current function.

In this chapter, we will discuss the following topics:

  • Applying the first-class function and higher-order function so that our functions can not only be invoked as a function, but also be assigned to any variable, pass a function, and return a function
  • Pure function, to avoid side effect in our function since it no longer contacts an outside state
  • Currying, as mentioned at the beginning of this chapter...

Applying the first-class function in all functions

The first-class function is just a normal class. We can treat the first-class function like any other data type. However, in the language that supports the first-class function, we can do the following tasks without invoking the compiler recursively:

  • Passing a function as another function's parameter
  • Assigning functions to variables
  • Storing functions in collections
  • Creating new functions from the existing functions at runtime

Fortunately, C++ can be used to solve the preceding tasks. We will discuss it in depth in the following topics.

Passing a function as another function's parameter

Let's start to pass a function as the function parameter. We will choose...

Getting acquainted with three functional techniques in the higher-order function

We discussed that in the first-class function, the C++ language treats the functions as the value, which means we can pass them to the other functions, assign to variables, and so on. However, we have another term in functional programming, that is, a higher-order function, which are functions that work on other functions. It means the higher-order function can pass functions as the argument and can also return a function.

The higher-order function concept can be applied to the function in general, like in a mathematical function, instead of the first-class function concept that can only be applied in the functional programming language. Now, let's examine the three most useful higher-order functions in functional programming--map, filter, and fold.

...

Avoiding the side effect with pure function

A pure function is a function that will always return the same result every time it is given the same input. The result doesn't depend on any information or state and won't produce a side effect, or a change of the system state outside of the function. Let's take a look at the following piece of code:

    /* pure_function_1.cpp */
#include <iostream>

using namespace std;

float circleArea(float r)
{
return 3.14 * r * r;
}

auto main() -> int
{
cout << "[pure_function_1.cpp]" << endl;

// Initializing a float variable
float f = 2.5f;

// Invoking the circleArea() function
// passing the f variable five times
for(int i = 1; i <= 5; ++i)
{
cout << "Invocation " << i << " -> ";
cout...

Reducing a multiple arguments function with currying

Currying is a technique to split a function that takes multiple arguments into evaluating a sequence of functions, each with a single argument. In other words, we create other functions based on a current function by reducing the current function. Let's suppose we have a function named areaOfRectangle(), which takes two parameters, length and width. The code will be like this:

    /* curry_1.cpp */

#include <functional>
#include <iostream>

using namespace std;

// Variadic template for currying
template<typename Func, typename... Args>
auto curry(Func func, Args... args)
{
return [=](auto... lastParam)
{
return func(args..., lastParam...);
};
}

int areaOfRectangle(int length, int width)
{
return length * width;
}

auto main() -> int
{
...

Summary

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...

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Key benefits

  • Modularize your applications and make them highly reusable and testable
  • Get familiar with complex concepts such as metaprogramming, concurrency, and immutability
  • A highly practical guide to building functional code in C++ filled with lots of examples and real-world use cases

Description

Functional programming allows developers to divide programs into smaller, reusable components that ease the creation, testing, and maintenance of software as a whole. Combined with the power of C++, you can develop robust and scalable applications that fulfill modern day software requirements. This book will help you discover all the C++ 17 features that can be applied to build software in a functional way. The book is divided into three modules—the first introduces the fundamentals of functional programming and how it is supported by modern C++. The second module explains how to efficiently implement C++ features such as pure functions and immutable states to build robust applications. The last module describes how to achieve concurrency and apply design patterns to enhance your application’s performance. Here, you will also learn to optimize code using metaprogramming in a functional way. By the end of the book, you will be familiar with the functional approach of programming and will be able to use these techniques on a daily basis.

Who is this book for?

This book is for C++ developers comfortable with OOP who are interested in learning how to apply the functional paradigm to create robust and testable apps.

What you will learn

  • • Get to know the difference between imperative and functional approaches
  • • See the use of first-class functions and pure functions in a functional style
  • • Discover various techniques to apply immutable state to avoid side effects
  • • Design a recursive algorithm effectively
  • • Create faster programs using lazy evaluation
  • • Structure code using design patterns to make the design process easier
  • • Use concurrency techniques to develop responsive software
  • • Learn how to use the C++ Standard Template Library and metaprogramming in a functional way to improve code optimization

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Aug 10, 2017
Length: 304 pages
Edition : 1st
Language : English
ISBN-13 : 9781787281974
Vendor :
Microsoft
Category :
Languages :

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Product Details

Publication date : Aug 10, 2017
Length: 304 pages
Edition : 1st
Language : English
ISBN-13 : 9781787281974
Vendor :
Microsoft
Category :
Languages :

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Table of Contents

8 Chapters
Diving into Modern C++ Chevron down icon Chevron up icon
Manipulating Functions in Functional Programming Chevron down icon Chevron up icon
Applying Immutable State to the Function Chevron down icon Chevron up icon
Repeating Method Invocation Using Recursive Algorithm Chevron down icon Chevron up icon
Procrastinating the Execution Process Using Lazy Evaluation Chevron down icon Chevron up icon
Optimizing Code with Metaprogramming Chevron down icon Chevron up icon
Running Parallel Execution Using Concurrency Chevron down icon Chevron up icon
Creating and Debugging Application in Functional Approach Chevron down icon Chevron up icon

Customer reviews

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Rating distribution
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.3
(6 Ratings)
5 star 16.7%
4 star 33.3%
3 star 33.3%
2 star 0%
1 star 16.7%
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Christian Albaret Feb 16, 2024
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I bought 5 books at once and could only give a fast glance at this one in order to write he review. It seems I have to write the reviews in order. I have been developping a lot in C++, and also used modern features of C++11 and above. The book discusses and shows examples on how to use these modern features. The advanced features are difficult to grasp: short examples don;t show enough, long examples are hard to read. The example in the book are fairly long, but they are given with detailed explanations.
Feefo Verified review Feefo
Mike Jan 05, 2018
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The grammar issue is bad but the author still manages to make himself understood. The content is decent but not worth the price.
Amazon Verified review Amazon
John Carter Sep 21, 2018
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
Very difficult to get to get to grips with initially but gets easier as you go.
Amazon Verified review Amazon
Hangzhou Tang May 31, 2018
Full star icon Full star icon Full star icon Empty star icon Empty star icon 3
It's not as perfect as I assume before. I found an error even in the beginning of the book. For example in page 11, the book shows "auto main ->int" which should be "auto main() -> int".
Amazon Verified review Amazon
Jonathan Apr 22, 2018
Full star icon Full star icon Full star icon Empty star icon Empty star icon 3
Grammar is terrible. Code snippets are duplicated over and over again - concepts that can be shown in one or two lines are surrounded by 20 lines of boilerplate.Coming from functional programming languages, I was excited for what might be possible in c++ but was disappointed by the lack of depth in the book. I don't know enough about c++ to say that's the author's fault or the language's.
Amazon Verified review Amazon
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