Preface

Programming styles, also known as coding styles or code styles, are sets of rules or guidelines that govern the templating of source code. These styles help programmers read and understand code, maintain it, and reduce the likelihood of introducing errors. Let’s explore functional programming as one of them. It is a paradigm that emphasizes treating data processing as resembling mathematical functions. In other words, functions are first-class citizens in functional programming. Functional programming is recognized as a foundation for processing external structural data governed by a Database Management System (DBMS). The DBMS is software executed atop an appropriate platform or technology used to organize, store, retrieve, and manipulate data in an organized manner.

Because DBMS handles concurrent access to data, thanks to functional programming data consistency can be protected by reducing side effects. While managing data using DBMS the following operation may be distinguished:

• Insert: Add new data to repository

• Update: Modify existing repository

• Delete: Remove data from repository

• Select: Retrieve data from repository

The operations are described by a Domain-specific Language (SQL for example) and executed by the DBMS. Functional programming constructs of the main programming language are a good candidate to be used as an equivalent solution to define these operations that can be integrated with the rest of the program. Let's delve into the details of this approach.

Functional programming is a style of developing the computer programs that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data. A mutable data is an object whose state can be modified after it is created. An immutable object is an object whose state cannot be modified after it is created.

The most important behavior of a function in the context of functional programming paradigm is that its output value depends only on the actual parameter values that are passed to while calling it. In other words, the function behavior doesn't depend on the local or global state. So calling a function f twice with the same value for a parameter x produces the same result f(x) each time. An example of the function conforming to this paradigm is for example:

    public static bool StringIsLongPredicate(string stringToTest)
    {
      return stringToTest.Length > 10;
    }

This predicate returns always true if the current string assigned to stringToTest is longer than 10. It represents the method that defines a set of criteria and determines whether the specified object meets those criteria. It eliminates side effects, which is one of the key motivations for using the functional programming approach to manage external data. In this scenario, the function can be sent and executed by a data management system and produce a set of related data.

Object-oriented languages, including but not limited to C#, incorporate several features that contribute to functional programming. Let’s explore some of these constructs:

• delegate and events - delegates are a fundamental construct in C# that enables late binding scenarios allowing the definition of a type-safe reference to a method; an event is essentially a delegate with additional restrictions

• extension methods - the extension method to use for static methods invocation syntax similar to the invocation of type members methods and finally cascading execution chain

• anonymous functions - allow definition and use of inline methods that don't have names

In programming languages, inline method definitions refer to a technique where the method header and its block of statements are located directly as an operand of expression where it is to be executed contributing to the evaluated result, rather than being defined in advance as a separate named construct (named block). As a result the method definition is unnamed. The main goal is to compress the whole expression to one line of code.

Check out the sections Functional(Programming Implementation to get more about available examples.

Check out the sections Extension Methods and Anonymous Functions to learn more on these concepts, which booth contributes to the Language Integration Query (LINQ) concept. The LINQ concept will be examined in detail as a main topic contributing to the Structural Data section.