bear/README.MD

# vuurraaf/v

A complete toolchain for **VuurRaaf**, written in V from scratch: a compiler,
an assembler, a linker, and a stack-based runtime. Everything — including the
object file format and the virtual machine — lives in this repository.

```
.vr  --compiler-->  .vobj  --linker-->  .vbin  --vm-->  output
.vasm --assembler--> .vobj
```

## Build

Requires [V](https://vlang.io) (`v` in your PATH).

```bash
v -o bin/vr .        # build the toolchain
./bin/vr up          # or rebuild from inside the toolchain
./bin/vr symlink     # optionally symlink bin/vr into your PATH
```

> Note: build with `v .` from the project root. Building via an explicit file
> or path argument makes V pick tcc without the Boehm GC, a combination that
> miscompiles this codebase (`vr up` already does the right thing).

## Usage

```
vr compile <file.vr> [-o out.vobj]          source  -> object
vr assemble <file.vasm> [-o out.vobj]       assembly -> object
vr link <a.vobj> [more.vobj ...] [-o out]   objects -> executable (.vbin)
vr run <file.vr|file.vbin>                  compile+link+run, or run a binary
vr debug <file.vr|file.vbin>                run with an instruction trace
vr test <file.vr>                           run every test_* function
vr bench <file.vr> [iterations]             benchmark main()
vr clean                                    remove .vobj/.vbin artifacts
vr up                                       rebuild bin/vr
vr symlink                                  link bin/vr into your PATH
vr config [set <key> <value>]               toolchain config (outdir, verbose)
vr info | loader | alloc | version | help
```

Quick start:

```bash
./bin/vr run examples/hello.vr        # run a program
./bin/vr test examples/tests.vr       # run the tests (one fails on purpose)
./bin/vr debug examples/hello.vr      # watch every bytecode instruction

# the assembler path
./bin/vr assemble examples/math.vasm -o math.vobj
./bin/vr link math.vobj -o math.vbin
./bin/vr run math.vbin

# multi-file programs (functions in one file may call functions in another)
./bin/vr compile examples/lib.vr -o lib.vobj
./bin/vr compile examples/use_lib.vr -o use_lib.vobj
./bin/vr link lib.vobj use_lib.vobj -o use_lib.vbin
./bin/vr run use_lib.vbin
```

## The VuurRaaf language

A small, V-flavored language. Values are 64-bit integers, strings, arrays, or
structs (strings concatenate with `+` and compare with `==`/`!=`; arrays and
structs are mutable references that compare by identity).

```
fn sum(items) {
    let total = 0
    for x in items {            // iterate an array
        total = total + x
    }
    return total
}

fn main() {
    let x = 6 * 7
    assert x == 42
    let big = x > 40 and x < 50 // and / or / not, short-circuiting
    if big {
        println("x is big")
    } else {
        println("x is small")
    }

    let a = [10, 20, 30]
    a[1] = 99                    // index assignment
    push(a, 40)                  // grow in place
    println(a)                   // [10, 99, 30, 40]
    println(len(a))              // 4
    println(sum(a))              // 179

    for i in 0..5 { ... }        // 0 1 2 3 4   (exclusive ..)
    for i in 1...3 { ... }       // 1 2 3       (inclusive ...)

    for i in 0..10 {
        if i == 2 {
            continue             // skip this iteration
        }
        if i == 5 {
            break                // leave the loop early
        }
    }

    let grid = [[1, 2], [3, 4]]  // nested arrays
    println(grid[1][0])          // 3

    let i = 100
    for i in 0..3 { ... }        // loop vars are scoped to the loop
    println(i)                   // 100

    if score >= 90 {             // else-if chains
        grade = "A"
    } else if score >= 80 {
        grade = "B"
    } else {
        grade = "F"
    }

    match day {                  // match on any comparable value
        "sat" {
            println("weekend")
        }
        "sun" {
            println("weekend")
        }
        else {                   // optional fallback arm
            println("workday")
        }
    }

    let pt = { x: 3, y: 4 }      // struct literal: { name: value, ... }
    println(pt.x)                // 3 — field access
    pt.y = 5                     // field assignment
    let p = { name: "amy", addr: { city: "nyc" } }  // nested structs
    println(p.addr.city)         // nyc
}
```

- functions: `fn name(a, b) { ... }` with `return expr`
- variables: `let name = expr`, reassignment `name = expr`
- arrays: `[e1, e2, ...]`, indexing `a[i]` (read and write), `len(a)`,
  `push(a, v)`; array literals may nest
- for loops: `for x in arr { }` and ranges `for i in 0..10 { }` /
  `for i in 0...10 { }`; loop variables are scoped to the loop body
- `break` / `continue` inside `while` and `for` loops (in `for` loops
  `continue` advances the loop variable / iterator first)
- else-if chains: `if a { } else if b { } else { }`
- `match`: `match expr { v1 { } v2 { } else { } }` — arms test equality on
  any comparable value (ints, strings, ...); the `else` arm is optional
- structs: literals `{ name: value, ... }` (may nest and may be empty `{}`),
  field access `a.b` and assignment `a.b = v` (chained: `a[i].b`, `a.b[i]`);
  structs are mutable references (identity `==`/`!=`), and setting a missing
  field adds it, so records can be built incrementally
- operators: `+ - * / %`, `== != < <= > >=`, `and or not`, unary `-`
- statements: `let`, assignment, `if/else`, `match`, `while`, `for`,
  `break`, `continue`, `return`, `assert`, calls, `print(...)` / `println(...)`
- comments: `//`

## Assembly

`.vasm` files talk to the VM directly. Labels, `.global` exports, and the full
opcode set:

```
; comment
.global main
main:
    push_int 42
    call helper 1        ; call <target> <argc>
    println
    halt

.global helper
helper:
    enter 0              ; reserve extra locals (args were copied in by `call`)
    load 0
    retv
```

Opcodes: `halt push_int push_str load store pop dup add sub mul div mod neg
eq ne lt le gt ge and or not jmp jz jnz call ret retv print println assert
enter mkarray aget aset alen apush mkstruct sget sset`.

Struct opcodes: `mkstruct n` pops `n` (name, value) pairs and pushes a struct
handle; `sget "field"` / `sset "field"` read/write a named field (pushing the
field name as a string first, exactly like the compiler does).

## Formats

- **VROBJ** (`.vobj`) — linker input: bytecode, exported symbols (function
  name -> code offset), string constants, and relocations (call sites and
  string references).
- **VRBIN** (`.vbin`) — the executable: function table, string table, bytecode.

## Architecture

| module       | role                                                        |
|--------------|-------------------------------------------------------------|
| `compiler/`  | lexer, recursive-descent parser, bytecode codegen (VROBJ)   |
| `assembler/` | `.vasm` -> VROBJ                                            |
| `linker/`    | resolves relocations, rebases strings, emits VRBIN          |
| `vm/`        | stack VM: tagged values, call frames, string/array heaps    |
| `obj/`       | VROBJ/VRBIN binary formats                                  |
| `bin/`       | small standalone tools: `tl_alloc.v`, `tl_loader.v`         |

The VM is a stack machine with 64-bit tagged values using two tag bits:
numbers are stored shifted left by two, string handles end in `01`, array
handles in `11` — so no integer ever collides with a heap handle. Arrays live
in a growable heap (`mkarray`/`aget`/`aset`/`alen`/`apush`). Calls push a
frame (return address, base pointer, argc), copy arguments into local slots,
and reserve extra locals with `enter n`. `vr debug` prints every instruction
with the stack contents (arrays rendered as `[1, 2, ...]`).

## Repository layout

```
main.v               CLI entry point (vr <command> ...)
v.mod                module definition
compiler/ assembler/ linker/ vm/ obj/   the toolchain itself
bin/                 built binary + standalone tools
examples/            runnable examples (hello, lib, asm, tests, fib)
```