HelloWorld.fs

 open System
printfn "Hello, World!"

F sharp Online Compiler

Write, Run & Share F# code online using OneCompiler's F# online compiler for free. It's one of the robust, feature-rich online compilers for F# language, running on the latest version 4.0. Getting started with the OneCompiler's F# compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as F# and start coding.

Read inputs from stdin

OneCompiler's F# online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample F# program which takes name as input and prints hello message with your name.

open System
let name = Console.ReadLine()
Console.Write("Hello 0.\n", name)

About `F#`

F#(F sharp) is a functional programming language which was developed by Microsoft in the year 2005. F# is .net implementation of OCaml. It can be used in variety of applications like graphic designing, Telecommunications, AI, CPU design, compiler programming, web applications, games etc.,

Syntax help

Data Types

Integer Data types

Data type	Description	Size	Range
sbyte	8-bit signed integer	1 byte	-128 to 127
byte	8-bit unsigned integer	1 byte	0 to 255
int16	16-bit signed integer	2 bytes	-32768 to 32767
unit16	16-bit unsigned integer	2 bytes	0 to 65,535
int/int32	32-bit signed integer	4 bytes	-2,147,483,648 to 2,147,483,647
uint32	32-bit unsigned integer	4 bytes	0 to 4,294,967,295
int64	64-bit signed integer	8 bytes	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
uint64	64-bit unsigned integer	8 bytes	0 to 18,446,744,073,709,551,615
bigint	arbitrary precision integer	At least 4 bytes	Integers

Float Data types

Data type	Description	Size	Range
float32	32-bit signed floating point number	4 bytes	±1.5e-45 to ±3.4e38
float	64-bit signed floating point number	8 bytes	±5.0e-324 to ±1.7e308
decimal	128-bit signed floating point number	16 bytes	±1.0e-28 to ±7.9e28

Text and Boolean Data types

Data type	Description	Size	Range
char	single character	2 bytes	U+0000 to U+ffff
string	Text	20 + (2 * length of the string) bytes	0 to up to 2 billion characters
bool	Stores either true or false	1 byte	True or false

Variables

Variable is a name given to the storage area in order to manipulate them in our programs.

let variable_name:data-type = value

Mutable variable declaration

let mutable variable_name:data-type = value

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition or set of conditions then If or IF-ELSE or Nested If-Elif-Else are used.

If

if conditional-expression then
   // code

If-Else

if conditional-expression then
   // code
else 
   // code

Nested If-Elif-Else

if conditional-expression then
  // code
elif conditional-expression then
   // code
elif conditional-expression then
   // code
...
else
   // code

2. For:

For loop is used to iterate a set of statements based on a condition.

For..to

Iteration occurs in ascending order

for var = start-expression to end-expression do
  // code

For...down-to

Iteration occurs in descending order.

for var = start-expression downto end-expression do
  // code

For..in

This loops is used when iteration occurs over enumerable collection like arrays, lists, sequences, range expression etc.

for pattern in enumerable-collection-expr do
   // code

Example

let listItems = [1,2,3,4,5]
for x in listItems do
   printfn "%d" x

3. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while condition-expr do   
 // code

Function

In F#, You can declare and use functions similar to Variables. In simpler words, you can understand them as user-defined variables.

How to define a function

let [inline] function-name parameter-list [ : return-type ]
   = function-body

How to call a function

let VarName = function-name parameter-list