Effects

Rellum marks effectful operations with !.

An effect is not hidden inside an ordinary expression. Reading files, receiving network data, writing output, and calling request effects are all visible in the program.

main! = {
    print!("hello")
}

Effect Bodies

Effect bodies are where output happens. They run after the reactive state for the tick has been advanced.

This keeps pure dataflow and side effects separate enough for the compiler to reason about both.