The Concept of Functions And Variables in F#

Functions

F# is a functional programming language that came with Visual Studio 2010. Functional programming is a programming paradigm that treats computations as the evaluations of mathematical functions. A function is a central point of a functional language. Functions are a first class part of the F# type system. It can perform an action, produce a value and define a purpose. Functions play an important role throughout the language; for example the type "char-> int" represents a F# function that takes a char and returns an int.

A Function is a type that gives the name functional programming to F#. Functions can be used in the same way as any other type. They can be given as an argument to other functions or returned from a function as a result and the function's type can be used as a Type argument to generic types. For example you can create a list of Functions. Although unlike .Net delegates, F# functions have the following two important differences:

The first difference is that Functions are not Nominal. Any Function that takes a char and returns an int is of Type "char-> int" whereas multiple differently named delegates may be used to represent functions of this signature and are not interchangeable.
The second difference is that Functions are designed to efficiently support either partial or full application.

The F# language provides many already created Functions, referred to as built-in Functions. printfn is one of the built-in Functions in F#.

Example-

// Built-in Function Example

printfn "This is showing Built-in Function"

Example

To declare a Function in F# we use the Let keyword.

// Function Example for addition substraction

let add a b = a + b
let sub a b = a - b
let printThreeNumbers number1 number2 number3 =
printfn "number1: %i" number1
printfn "number2: %i" number2
printfn "number3: %i" number3
printThreeNumbers 6 (add 42 6) (sub 42 6)

Output-

Example-

let sqr x = x*x;;
let y= sqr 5;;
printfn "%d"y;;
System.Console.ReadKey(true);

Output-

Variables

A variable is a section of the computer's memory used to temporarily hold a value. Declaring a variable means that the variable has been reserved a portion of memory. The variable can be changed if you rpovide the Mutable keyword for that variable. In F# a Mutable variable has limited scope, either as a field of a type or as a local value. Mutable variables with a limited scope are easier to control and less likely to be modified in an incorrect manner.

To declare a variable, use the let operator, followed by a name for the variable and assign a value to it using the assignment operator "=". The Syntax for declaring a Variable is:

let VariableName= Value
Example-

let a = 2

You can also use a semicolon at the end for termination. A semicolon is optional.

let a = 2;
We declare and initialize a variable in one line, but if you want you can initialize it in next line.

let a =
2
Or you can use semicolan.

let a =
2;
Example-

//Variable Example
let a = 6
let b = 5
let c = a+ b
printfn "a: %i" a
printfn "b: %i" b
printfn "c: %i" c
Output-

Example-
Showing an integer variable:

let x = 5;
printfn "%d"x;;
System.Console.ReadKey(true);
Output-

Summary
In this article I have covered Functions and Variables.