Welcome to XCODX Online Compiler
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Haskell is a purely functional programming language built around lazy evaluation and a static type system with full type inference. It was designed by a committee of academics beginning in 1987 and named after the logician Haskell Curry, with the first standardized version published in 1990. Functions have no side effects by default, and effects such as input and output are tracked in the type system through the IO type, which makes code predictable to reason about and to refactor. GHC, the Glasgow Haskell Compiler, is the de facto standard implementation, and Haskell shows up today in compilers, financial systems, and correctness-sensitive tooling, from Cardano's Plutus contracts to Meta's spam-fighting engine. On XCODX, Haskell runs in a cloud sandbox with GHC, so you can try the language and its base library without installing a compiler or a build tool.
-- Compiled with GHC: pure functions plus IO for input and output
main :: IO ()
main = do
putStrLn "What is your name?"
name <- getLine
putStrLn ("Hello, " ++ name ++ "!")
let squares = map (^ 2) [1 .. 5]
putStrLn ("First five squares: " ++ show squares)Haskell's strengths are its type system and purity: the compiler rejects a large class of mistakes before the program runs, and equational reasoning makes refactoring predictable. Reach for it when correctness matters more than raw development speed, such as parsers, compilers, domain-specific languages, and concurrent services that benefit from its guarantees. Lazy evaluation also expresses infinite data structures and streaming pipelines cleanly. It is a poor fit when you need tight, predictable memory and latency without careful tuning, since laziness can introduce space leaks that take experience to diagnose.
getLine reads one line as a String, getContents reads the whole stream lazily, and interact maps a function over all of standard input. On XCODX you can type into the live terminal, where the program pauses at getLine until you press Enter, or paste everything into the Stdin Box before running. Pressing Ctrl+D closes the stream so getContents and interact can finish.
No. The sandbox compiles a single file with GHC against the base library only, and it has no network access. There is no cabal or stack and no Hackage download, so third-party packages are unavailable; use modules that ship in base, such as Data.List, Data.Char, Data.IORef, and Text.Printf.
Compiled. GHC produces an executable that then runs, so type errors are reported at compile time before any output appears. This differs from GHCi, the interactive REPL, which the run button does not use.
getLine and getContents block until input arrives, so if nothing is sent and the stream stays open, the program waits. Provide input through the Stdin Box or the live terminal, and close the stream with Ctrl+D so functions that read to end-of-input can return.
No. The filesystem is temporary and reset on every run, and there is no network access. Programs that open sockets, fetch URLs, or expect data to persist between runs will not work, so rely on stdin and stdout instead.
The GHC version is shown in the badge next to the editor. It is free with no signup and no local install, and each run starts from a fresh sandbox with no saved files.
main.hshaskellgetLinemain :: IO ()
main = do
putStrLn "Hello from Haskell!"
putStrLn "Welcome to XCODX Online Compiler!"
let message = "Haskell is elegant!"
putStrLn message