Introduction: The looping concept is
introduced in programming to repeatedly execute several lines of code for
specific numbers of time. Generally lines of code execute one-by-one, meaning one
line then another line then another and so on. When we need to execute a specific
line of codes repeatedly for a certain time, then we can use looping concept. Loops
are also referred as repetition or iteration. Now, we try to understand looping
concepts in FSharp. We start with a simple While loop.
while Loop: The body of while loop is executed until given the conditional
expression evaluates to false. At first, the given condition is evaluated, if the condition is true then the body of the loop is executed then again the condition is
evaluated. This process continues till condition is true. Its syntax is given
below
while condition_exp do
body of loop
Write the following code in a F# application.
//while
loop
let
mutable i=0
while i<10
do
i<- i+1
printfn " %d" i
Run the application, the
output will look like below:
For Loop: We use a for loop when there is a need to execute several lines of
code for a fixed number of times.
Simple For Loop: In a simple for loop, the start and end
value is specified. The body of the for loop is iterated till the counter is less than
the end value. Its syntax is given below
for identifier=start_value to/downto end_value do
body of for loop
We write the following code.
//simple for loop using to
for
i=1 to 10 do
printfn " %d" i
Run the application, the output will look like below:
We write the following code.
//simple
for loop using downto
for i=10
downto 1 do
printfn " %d" i
The output will look like the below figure:
For Loop With Collections:
In F#, a for loop is also used with collections. It acts the same as foreach in C#. Its syntax is given below
for pattern in Exp do
body of loop
For Loop with List:
//for loop with list
let simplelist=[2;4;6;8;10]
for i
in simplelist do
printfn " %d" i
The output will look like as below
figure:
For Loop With Array:
//for
loop with array
let arr=[|1;2;3;4;5|]
for i
in arr do
printfn " %d" i
The output will look like
below:
For Loop With Integer Range:
//for
loop with integer range
for i
in 1..5 do
printfn " %d" i
The output will look like below:
For Loop With character Range:
//for loop with character range
for i
in 'a'..'e'
do
printfn " %c" i
Output will look like below: