Raft

Run a program to see what it prints.

Writing Raft

Raft is postfix and stack-based: operands first, then the instruction that consumes them. 5 3 - pushes 5 and 3 and leaves 2. # and // start a comment. A name beginning with a dot is a label — .loop marks a spot, and Jump .loop goes there.

Instruction set

Literals

42 -3.14 true false "a string"

Arithmetic

+ - * / % ^ — or by name: Add Sub Mul Div Mod Exp Neg

Comparison

Eq Ne Lt Le Gt Ge — each leaves a boolean. Ordering needs two integers or two floats; equality is defined for any pair.

Logic

Not And Or — operands are booleans, and neither side short-circuits.

Stack

Pop Dup Swap

Variables

StoreVar 0 LoadVar 0 — slots are numbered, not named.

Control flow

Jump .label JumpIfFalse .label Call .label Return

Strings and arrays

PushString "hi" MakeString hi StringConcat MakeArray 3 ArrayGet ArraySet

Modules

MakeModule 1 name ModuleGet name ModuleSet name LoadGlobal io GetExport print

Native calls

io.print CallNative 1 — io.print loads the standard io module's export, and CallNative calls it with that many arguments from the stack.

Actors

SpawnActor .body SendMessage ReceiveMessage — spawning leaves the actor on the stack; sending takes a message below it and leaves the actor there to send again.

Supervision

SpawnSupervisor .body SetStrategy 0|1|2 SuperviseChild <address> RestartChild <address> — strategies are one-for-one, one-for-all and rest-for-one.

How this page runs your program

This is the VM from the repository compiled to WebAssembly, not a reimplementation: the same compiler, the same opcodes, the same heap and garbage collector. It runs in a worker under an instruction budget, and the page stops a run that outlasts its stopwatch, so a program that loops forever costs you a message rather than the tab.