# Understanding the Functional Programming Basics

Understanding the Functional Programming and its Uses

## Introduction

Employers nowadays are searching for programmers who can solve problems using a variety of paradigms. Functional programming, in particular, is gaining popularity as a solution to modern problems due to its simplicity and scalability. Let’s dig into more details on it.

## What is Functional Programming?

It is a programming framework in which everything is bound using pure mathematical functions. It’s a declarative programming approach. In comparison to an imperative model, which focuses on “how to solve,” it emphasises “what to solve.”

Instead of statements, it employs expressions. A statement is executed to assign variables, while an expression is evaluated to generate a value. Such functions have certain unique characteristics, which are discussed further down.

## Foundation of Functional Programming

Lambda Calculus is the foundation of it. Alonzo Church developed the lambda calculus method to research computations with functions. It is known as the world’s smallest programming language. In terms of computation, it is comparable to a Turing machine.

It establishes a theoretical framework for defining and evaluating functions. Almost all existing functional programming languages are built on top of it.

Programming Languages that support functional programming: Haskell, JavaScript, Scala, Erlang, Lisp, ML, Clojure, OCaml, Common Lisp, Racket.

## Concepts of Functional Programming

### Pure functions

If a function always returns the same result for the same argument values and has no side effects such as changing an argument (or global variable) it is called a pure function. The return value is the only result that you get when you call a pure function. The “pure” attribute in GCC can be used to label functions as pure.

``````calculate(a,b)       //calculate is taking a and b as arguments
return a-b      //calculate is returning difference of a and b without changing them``````

### Recursion

Recursion is the mechanism of a function calling itself directly or indirectly, and the resulting function is known as a recursive function. Certain problems can be solved quickly using the recursive algorithm.

The idea is to break down a problem into smaller problems and then apply one or more base conditions to stop the recursion. Calculation of factorial of a number can be done through an interactive approach as well as using recursion. However, the recursive method is a better solution for this task.

Code snippet for calculating factorial using recursion:

``````fact(value)
if(value>=1)
return value*fact(value-1)
else
return 1``````

There are no “for” or “while” loops in functional languages. Recursion is used to implement iteration in functional languages. Recursive functions call themselves over and over before they reach the base case.

### Referential transparency

Variables specified in functional programmes do not alter their value in the programme. Assignment statements are not used in functional systems. We define new variables only when we need to store a value.

Since any attribute can be replaced with its actual value at any stage during execution, there are no side effects. Any variable’s state is constant at all times.

### Functions are First-Class and can be Higher-Order

First-class functions are handled the same as first-class variables. Variables of the first class may be passed as parameters to functions, returned from functions, or stored in data structures. Higher-order functions are those that accept other functions as arguments and may also return them.

Higher-order functions and first-class functions are similar in that they both accept functions as arguments and outcomes of other functions. The distinction is subtle: “higher-order” refers to a mathematical concept of functions that operate on other functions, while “first-class” refers to programming language entities with no restrictions on their use. Thus, first-class functions can appear anywhere in the program where other first-class entities like numbers can, including arguments to other functions and their return values.

### Variables are Immutable

We can’t change a variable after it’s been initialized in it. We can create new variables but not change existing variables, which is very useful for maintaining a state during a program’s runtime. We can be certain that once we construct a variable and set its value, the value of that variable will never change.

• Pure functions are simpler to comprehend because they do not alter their states and rely solely on the feedback they receive. Their function signature contains all relevant information, such as their return type and arguments.
• The languages’ ability to handle functions as values and transfer them as parameters to functions makes the code more readable and understandable.
• It is simpler to test and debug. Since they use immutable values, it’s easier to spot flaws in programmes written with pure functions.
• Pure functions do not modify variables or any other data outside of them, so they are used to enforce concurrency/parallelism.
• It employs lazy evaluation, which avoids repeated evaluation by evaluating and storing the value only when it is needed.

Now that you have understood Functional programming concepts, let me show you the advantages and disadvantages of Functional programming.

• When writing pure functions, the readability of the code will suffer.
• It can be intimidating to write programmes in a recursive style rather than using loops.
• Pure functions are simple to write, but integrating them with the rest of the programme and I/O operations is difficult.
• Output may be harmed by immutable values and recursion.

## Applications of Functional programming

• Functional programming is used in mathematical computations.
• Functional programming is a great tool to be used where concurrency or parallelism is required.

What is a functional programming example?

Code having pure functions and recursions can be considered an example of functional programming.

What is the most popular functional programming language?

The popular functional programming languages include Haskell, Erlang etc. Haskell is without a doubt the most common functional programming language. It’s memory-safe, has great garbage collection, and is fast thanks to early machine code compilation. Elixir has carved out a name for itself as the best usable language for concurrent systems.

What is functional programming used for?

The applications of it include spreadsheets, research areas, mathematical computing, and even in some industries such as aerospace systems, hardware design, and web programming. It is also used in mathematical operations, AI pattern matching. To summarise functional programming can be used where a task can be broken down into a set of rules that has to be applied to get the output.

Is Python a functional programming language?

In comparison to Scala and JavaScript, Python supports it but only to a limited extent. As a multi-paradigm language, Python has some support for functional programming.

## Key Takeaways

Functional programming is a declarative programming model that uses sequential functions rather than statements to construct programmes. Each function takes an input value and returns a consistent output value, regardless of the programme state.

Its key features include recursion, use of pure functions, referential transparency etc. The advantages of functional programming include easy debugging, lazy evaluation, enhanced readability and modularity. It has a wide range of applications ranging from academics to solving industrial problems.