Introduction
Today I am discussing Arrays. Most
of us are familiar with the concept of arrays as they work in almost all
programming language. Arrays are a mutable collection type in F#. Here mutable
means the values in an array can be changed after the array has been created.
Arrays are ubiquitous; a familiar Data Structure used to represent a group
of related, ordered values. An array contain a zero based, fixed size mutable
sequence of consecutive data elements, all of the same type.
Arrays and Lists are both
collections but an array has a number of properties which makes Arrays
different from Lists. You can update the values which are in an Array but in a
List you cannot update. On the other hand a List can grow dynamically where as
Arrays can not grow. Different Arrays called by different names like one
dimensional arrays are referred as Vector and multidimensional are matrices.
You can define Arrays by Sequence of
Items which can be separated by Semicolons. When you create an Array this will
start by an opening square bracket and a Vertical bar([|) and end with a
vertical bar and a Closing Square Bracket(|]).
Create And Access Array
Arrays can be created in one of the
several ways. The general syntax for an array creation is as follows.
let ar=[| element1;element2;.......
or array comprehension |] //syntax for creating Array
You
can also put array items in separate lines; in that case the semicolon is
optional.
// Syntax for creating Arrays in separate lines
let ar=
[|
element1
element2
.......
elementn
|]
Defining
an Array literal
You
can define an Array literal in the same way as lists by placing the array
elements between this notation [||] like below.
//Defining an Array
let num=[|
"one";
"two";
"three";
"four"
|]
How
to Reference an Array
The
syntax for referencing an Array element is the name of the identifier of the
array followed by a dot (.) known as a period and then the index of the element
in Square brackets ([]) like below.
// syntax for referencing Array
let firstNum = num.[0]
let secondNum = num.[1]
let thirdNum = num.[2]
let fourthNum = num.[3]
How
to set the value of an Array Element
You
can set the value of an array element by left arrow and the value you want to
assign followed by the left arrow.
//Syntax for setting Values to array elements
num.[0] <- " abc,"
num.[1] <- " def,"
num.[2] <- " ghi,"
num.[3] <- " jkl "
Example-
Figure 1.
//example of array
let city = [|
"Delhi"
"Noida"
"Gaziyabad"
"Hapur"
|]
printfn "%s" city.[0] //Delhi
printfn "%s" city.[1] //Noida
printfn "%s" city.[2] //Gaziyabad
printfn "%s" city.[3] //Hapur
Output-
Figure 2.
Multidimensional
Array
A
multidimensional array can be defined as an Array of an Array. In F# a
multidimensional array is defined in two categories generally referred to
as a Jagged Array and a Rectangular array.
Jagged Array
A
Jagged Array is referred to as an Array of an Array where the inner array
is of a varying size, when written out showing an entire array in
"jagged" appearance. You can also say that the second dimension
is not in a regular shape.
Example-
Figure 3.
//example of jagged array
let num = [|[|1; 2; 3|]; [|4; 5; 6|]|]
let row = num.[0] // [|4; 5; 6|]
let elementone = row.[0] // 4
let elementtwo = num.[1].[0] // 4 â€" .operator used two times
printfn "%i %i" elementone
elementtwo
Output-
Figure 4.
Rectangular Array
A
rectangular array is an array which contains one or more other arrays and
all inner arrays are of the same length. The resulting data structure
is like a matrix or grid type.
Example-
Figure 5.
//example of Rectangular
array
// create a square array,
// initally start with zeros
let sqr = Array2D.create 2 2 0
// populate the array
sqr.[0,0] <- 1
sqr.[0,1] <- 2
sqr.[1,0] <- 3
sqr.[1,1] <- 4
// print the array
printfn "%A" sqr
Output-
Figure 6.