Welcome to XCODX Online Compiler
Quick Start:
Ctrl+Enter Run code
Ctrl+S Save / Download
Ctrl+L Clear output
Select a language and start coding.
F# is Microsoft's answer to the question 'what if ML met .NET?' Designed by Don Syme at Microsoft Research and now developed in the open, F# delivers succinct functional-first code — immutability by default, algebraic data types, pattern matching, the pipeline operator — with full access to the entire .NET ecosystem. F# 9 shipped alongside .NET 9 (November 2024) with nullable reference type interop and performance work. Production users include fintech and energy-trading firms, and features F# pioneered (records, pattern matching) have steadily migrated into C#. This variant compiles your code as a .NET program. The terminal on this page is fully interactive: Console.ReadLine waits for your real keystrokes while output streams live.
open System
printf "What's your name? "
let name = Console.ReadLine()
printfn "Hello, %s!" name
printf "Enter numbers separated by spaces: "
let numbers =
Console.ReadLine().Split(' ', StringSplitOptions.RemoveEmptyEntries)
|> Array.map float
numbers
|> Array.map (fun x -> x * x)
|> Array.sum
|> printfn "Sum of squares: %g"
let parity n = if n % 2 = 0 then "an even" else "an odd"
printfn "You entered %d values - %s count." numbers.Length (parity numbers.Length)F# appeals to two overlapping groups: .NET developers who want functional programming without leaving their platform, and functional programmers who need .NET's libraries and jobs. Practicing here covers what F# interviews and coursework emphasize — pipelines, discriminated unions, records, recursion, and Option handling — without installing the .NET SDK. It's also useful for C# developers evaluating F# for a data-processing or domain-modeling component, a common adoption path since both compile to the same IL and interoperate freely in one solution.
Yes. The compiled program runs attached to a live terminal, so Console.ReadLine blocks until you type a line, and printf/printfn output appears as it executes. You can chain several prompts — read a name, then numbers, then options — and watch each pipeline stage respond in real time.
This variant compiles your file as a .NET program and runs the resulting binary — full compilation, matching how production F# ships. The fsi variant evaluates your code through F# Interactive's script engine instead, which skips the build step. Same language and same results for typical code; choose fsi for quicker iteration.
No — execution is a single file with no NuGet restore, so external packages aren't available. What you do get is substantial: the entire .NET base class library (System.*, collections, LINQ from F#, regex, math) plus F#'s own FSharp.Core with List, Array, Seq, Map, Option, and Result modules.
main.fsmllikeConsole.ReadLine()// F# .NET Program
printfn "Hello from F#.NET!"
printfn "Welcome to XCODX Online Compiler!"
let numbers = [1..10]
let sum = List.sum numbers
let evens = List.filter (fun x -> x % 2 = 0) numbers
printfn "Numbers: %A" numbers
printfn "Sum: %d" sum
printfn "Evens: %A" evensThe .NET toolchain emits a spurious "Can't rename" line during compilation. It is suppressed on a successful build.