riki/rkgk
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introduce tags, structs, and reticles

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this was meant to be split into smaller changes, but I realised I edited my existing revision too late.
This commit is contained in:
りき萌 2024-09-08 13:53:29 +02:00
parent 8356b6c750
commit 5b7d9586ea
26 changed files with 1113 additions and 351 deletions
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108
crates/haku/src/bytecode.rs
View file

@ -12,6 +12,7 @@ pub enum Opcode {
Nil,
False,
True,
Tag,
Number, // (float: f32)
Rgba, // (r: u8, g: u8, b: u8, a: u8)
@ -36,6 +37,7 @@ pub enum Opcode {
// Control flow.
Jump, // (offset: u16)
JumpIfNot, // (offset: u16)
Field, // (count: u8, tags: [u16; count])
// Function calls.
Call, // (argc: u8)
@ -157,6 +159,12 @@ impl Chunk {
}
}
impl Offset {
pub fn to_u16(self) -> u16 {
self.0
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ChunkSizeError;
@ -193,21 +201,48 @@ impl DefId {
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
pub struct TagId(u16);
impl TagId {
pub(crate) fn from_u16(x: u16) -> Self {
Self(x)
}
pub fn to_u16(self) -> u16 {
self.0
}
}
#[derive(Debug, Clone)]
pub struct Defs {
defs: Vec<String>,
tags: Vec<String>,
}
#[derive(Debug, Clone, Copy)]
pub struct DefsLimits {
pub max_defs: usize,
pub max_tags: usize,
}
#[derive(Debug, Clone, Copy)]
pub struct DefsImage {
defs: usize,
tags: usize,
}
impl Defs {
pub fn new(capacity: usize) -> Self {
assert!(capacity < u16::MAX as usize + 1);
pub fn new(limits: &DefsLimits) -> Self {
assert!(limits.max_defs < u16::MAX as usize + 1);
assert!(limits.max_tags < u16::MAX as usize + 1);
let mut tags = Vec::with_capacity(limits.max_tags);
add_well_known_tags(&mut tags);
Self {
defs: Vec::with_capacity(capacity),
defs: Vec::with_capacity(limits.max_defs),
tags,
}
}
@ -219,14 +254,14 @@ impl Defs {
self.len() != 0
}
pub fn get(&mut self, name: &str) -> Option<DefId> {
pub fn get_def(&mut self, name: &str) -> Option<DefId> {
self.defs
.iter()
.position(|n| *n == name)
.map(|index| DefId(index as u16))
}
pub fn add(&mut self, name: &str) -> Result<DefId, DefError> {
pub fn add_def(&mut self, name: &str) -> Result<DefId, DefError> {
if self.defs.iter().any(|n| n == name) {
Err(DefError::Exists)
} else {
@ -239,9 +274,27 @@ impl Defs {
}
}
fn add_tag(tags: &mut Vec<String>, name: &str) -> Result<TagId, TagError> {
if tags.len() >= tags.capacity() {
return Err(TagError::OutOfSpace);
}
let id = TagId(tags.len() as u16);
tags.push(name.to_owned());
Ok(id)
}
pub fn get_or_add_tag(&mut self, name: &str) -> Result<TagId, TagError> {
if let Some(index) = self.tags.iter().position(|n| n == name) {
Ok(TagId(index as u16))
} else {
Self::add_tag(&mut self.tags, name)
}
}
pub fn image(&self) -> DefsImage {
DefsImage {
defs: self.defs.len(),
tags: self.tags.len(),
}
}
@ -249,6 +302,9 @@ impl Defs {
self.defs.resize_with(image.defs, || {
panic!("image must be a subset of the current defs")
});
self.tags.resize_with(image.tags, || {
panic!("image must be a subset of the current defs")
});
}
}
@ -266,3 +322,45 @@ impl Display for DefError {
})
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TagError {
OutOfSpace,
}
impl Display for TagError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(match self {
TagError::OutOfSpace => "too many tags",
})
}
}
macro_rules! well_known_tags {
($($ident:tt = $value:tt),* $(,)?) => {
impl TagId {
$(
#[allow(non_upper_case_globals)]
pub const $ident: Self = Self($value);
)*
}
fn add_well_known_tags(tags: &mut Vec<String>) {
$(
let id = Defs::add_tag(tags, stringify!($ident)).unwrap();
assert_eq!(id, TagId::from_u16($value));
)*
}
}
}
well_known_tags! {
// NOTE: The numbers must be sorted from 0 to N, due to limitations of Rust's macro system.
// https://github.com/rust-lang/rust/issues/83527
Nil = 0,
From = 1,
To = 2,
Num = 3,
}

37
crates/haku/src/compiler.rs
View file

@ -7,7 +7,9 @@ use alloc::vec::Vec;
use crate::{
ast::{Ast, NodeId, NodeKind},
bytecode::{Chunk, DefError, Defs, EmitError, Opcode, CAPTURE_CAPTURE, CAPTURE_LOCAL},
bytecode::{
Chunk, DefError, Defs, EmitError, Opcode, TagError, TagId, CAPTURE_CAPTURE, CAPTURE_LOCAL,
},
diagnostic::Diagnostic,
source::SourceCode,
system::{System, SystemFnArity},
@ -123,11 +125,6 @@ pub fn compile_expr<'a>(c: &mut Compiler<'a>, src: &Source<'a>, node_id: NodeId)
}
}
fn unsupported(c: &mut Compiler, src: &Source, node_id: NodeId, message: &str) -> CompileResult {
c.emit(Diagnostic::error(src.ast.span(node_id), message));
Ok(())
}
fn compile_nil(c: &mut Compiler) -> CompileResult {
c.chunk.emit_opcode(Opcode::Nil)?;
@ -183,7 +180,7 @@ fn compile_ident<'a>(c: &mut Compiler<'a>, src: &Source<'a>, node_id: NodeId) ->
c.chunk.emit_u8(index)?;
}
Ok(None) => {
if let Some(def_id) = c.defs.get(name) {
if let Some(def_id) = c.defs.get_def(name) {
c.chunk.emit_opcode(Opcode::Def)?;
c.chunk.emit_u16(def_id.to_u16())?;
} else {
@ -202,7 +199,8 @@ fn compile_ident<'a>(c: &mut Compiler<'a>, src: &Source<'a>, node_id: NodeId) ->
}
fn compile_tag(c: &mut Compiler, src: &Source, node_id: NodeId) -> CompileResult {
let tag = src.ast.span(node_id).slice(src.code);
let span = src.ast.span(node_id);
let tag = span.slice(src.code);
match tag {
"False" => {
@ -212,7 +210,17 @@ fn compile_tag(c: &mut Compiler, src: &Source, node_id: NodeId) -> CompileResult
c.chunk.emit_opcode(Opcode::True)?;
}
_ => {
c.emit(Diagnostic::error(src.ast.span(node_id), "uppercased identifiers are reserved for future use; please start your identifiers with a lowercase letter instead"));
let tag_id = c.defs.get_or_add_tag(tag).unwrap_or_else(|error| {
match error {
TagError::OutOfSpace => {
c.emit(Diagnostic::error(span, "too many unique tags used"));
}
}
TagId::Nil
});
c.chunk.emit_opcode(Opcode::Tag)?;
c.chunk.emit_u16(tag_id.to_u16())?;
}
}
@ -598,7 +606,7 @@ fn def_prepass<'a>(c: &mut Compiler<'a>, src: &Source<'a>, toplevel: NodeId) ->
if let (Some(ident), Some(op)) = (binary_walk.node(), binary_walk.get(NodeKind::Op)) {
if src.ast.span(op).slice(src.code) == "=" {
let name = src.ast.span(ident).slice(src.code);
match c.defs.add(name) {
match c.defs.add_def(name) {
Ok(_) => (),
Err(DefError::Exists) => c.emit(Diagnostic::error(
src.ast.span(ident),
@ -651,7 +659,12 @@ fn compile_def<'a>(c: &mut Compiler<'a>, src: &Source<'a>, node_id: NodeId) -> C
return Ok(());
};
if src.ast.kind(left) != NodeKind::Ident {
if src.ast.kind(left) == NodeKind::Tag {
c.emit(Diagnostic::error(
src.ast.span(left),
"defs may not be named with uppercase letters, because uppercase letters are used for tags",
));
} else if src.ast.kind(left) != NodeKind::Ident {
c.emit(Diagnostic::error(
src.ast.span(left),
"def name (identifier) expected",
@ -662,7 +675,7 @@ fn compile_def<'a>(c: &mut Compiler<'a>, src: &Source<'a>, node_id: NodeId) -> C
// NOTE: def_prepass collects all definitions beforehand.
// In case a def ends up not existing, that means we ran out of space for defs - so emit a
// zero def instead.
let def_id = c.defs.get(name).unwrap_or_default();
let def_id = c.defs.get_def(name).unwrap_or_default();
compile_expr(c, src, right)?;
c.chunk.emit_opcode(Opcode::SetDef)?;

1
crates/haku/src/lib.rs
View file

@ -12,5 +12,6 @@ pub mod render;
pub mod source;
pub mod system;
pub mod token;
pub mod trampoline;
pub mod value;
pub mod vm;

2
crates/haku/src/render.rs
View file

@ -127,7 +127,7 @@ impl<'a> Renderer<'a> {
&paint,
&SStroke {
width: stroke.thickness,
line_cap: LineCap::Square,
line_cap: LineCap::Round,
..Default::default()
},
transform,

140
crates/haku/src/system.rs
View file

@ -6,8 +6,8 @@ use core::{
use alloc::vec::Vec;
use crate::{
bytecode::Chunk,
value::Value,
bytecode::{Chunk, EmitError, Offset, Opcode, TagId},
value::{BytecodeLoc, Closure, FunctionName, Value, Vec4},
vm::{Exception, FnArgs, Vm},
};
@ -29,6 +29,7 @@ pub struct System {
pub resolve_fn: fn(SystemFnArity, &str) -> Option<u8>,
pub fns: [Option<SystemFn>; 256],
pub chunks: Vec<Chunk>,
structs_chunk_offsets: StructsChunkOffsets,
}
#[derive(Debug, Clone, Copy)]
@ -36,33 +37,28 @@ pub struct SystemImage {
chunks: usize,
}
macro_rules! def_fns {
($($index:tt $arity:tt $name:tt => $fnref:expr),* $(,)?) => {
pub(crate) fn init_fns(system: &mut System) {
$(
debug_assert!(system.fns[$index].is_none());
system.fns[$index] = Some($fnref);
)*
}
pub(crate) fn resolve(arity: SystemFnArity, name: &str) -> Option<u8> {
match (arity, name){
$((SystemFnArity::$arity, $name) => Some($index),)*
_ => None,
}
}
};
#[derive(Debug, Clone)]
struct StructsChunkOffsets {
dotter: BytecodeLoc,
}
impl System {
pub fn new(max_chunks: usize) -> Self {
assert!(
max_chunks > 1,
"the 0th chunk is allocated for internal purposes; therefore there must be more than one chunk to execute bytecode"
);
assert!(max_chunks < u32::MAX as usize);
let (structs_chunk, structs_chunk_offsets) = Self::structs_chunk().unwrap();
let mut system = Self {
resolve_fn: Self::resolve,
fns: [None; 256],
chunks: Vec::with_capacity(max_chunks),
structs_chunk_offsets,
};
system.chunks.push(structs_chunk);
Self::init_fns(&mut system);
system
}
@ -92,6 +88,64 @@ impl System {
panic!("image must be a subset of the current system")
});
}
// The structs chunk contains bytecode for _struct functions_.
//
// Struct functions are a way of encoding structures with arbitrary named data fields.
// They are called like regular functions, except they always expect a single tag-type
// argument. They're used where performance is not a primary concern---in structures that appear
// once or a couple times throughout the lifetime of a program, in which convenient,
// backwards-compatible field access is a priority.
//
// Each struct function has only two opcodes: `Field`, followed by a `Return`.
// The `Field` opcode is an efficient way of encoding an if chain made solely out of tag
// comparisons, returning a closure capture (or error if there's no field with the given name.)
//
// if (tag == A) capture_0
// else if (tag == B) capture_1
// else if (tag == C) capture_2
// else error
//
// Closure captures are used here, because they're a convenient way of attaching indexed data
// to any function, even created outside the language itself.
//
// All of this results in a function that can be called like `d From` to obtain a piece of data
// stored inside of the `d` structure.
fn structs_chunk() -> Result<(Chunk, StructsChunkOffsets), EmitError> {
let mut chunk = Chunk::new(128).unwrap();
let dotter = chunk.offset();
chunk.emit_opcode(Opcode::Field)?;
chunk.emit_u8(3)?;
chunk.emit_u16(TagId::From.to_u16())?;
chunk.emit_u16(TagId::To.to_u16())?;
chunk.emit_u16(TagId::Num.to_u16())?;
chunk.emit_opcode(Opcode::Return)?;
fn loc(offset: Offset) -> BytecodeLoc {
BytecodeLoc {
chunk_id: ChunkId(0),
offset: offset.to_u16(),
}
}
Ok((
chunk,
StructsChunkOffsets {
dotter: loc(dotter),
},
))
}
pub fn create_dotter(&self, from: Vec4, to: Vec4, num: f32) -> Closure {
Closure {
start: self.structs_chunk_offsets.dotter,
name: FunctionName::Anonymous,
param_count: 1,
local_count: 0,
captures: Vec::from_iter([Value::Vec4(from), Value::Vec4(to), Value::Number(num)]),
}
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
@ -105,11 +159,29 @@ impl Display for ChunkError {
impl Error for ChunkError {}
macro_rules! def_fns {
($($index:tt $arity:tt $name:tt => $fnref:expr),* $(,)?) => {
pub(crate) fn init_fns(system: &mut System) {
$(
debug_assert!(system.fns[$index].is_none());
system.fns[$index] = Some($fnref);
)*
}
pub(crate) fn resolve(arity: SystemFnArity, name: &str) -> Option<u8> {
match (arity, name){
$((SystemFnArity::$arity, $name) => Some($index),)*
_ => None,
}
}
};
}
pub mod fns {
use alloc::{format, vec::Vec};
use crate::{
value::{Fill, List, Ref, Rgba, Scribble, Shape, Stroke, Value, Vec2, Vec4},
value::{Fill, List, Ref, Reticle, Rgba, Scribble, Shape, Stroke, Value, Vec2, Vec4},
vm::{Exception, FnArgs, Vm},
};
@ -181,8 +253,11 @@ pub mod fns {
0xc1 Nary "line" => line,
0xc2 Nary "rect" => rect,
0xc3 Nary "circle" => circle,
0xe0 Nary "stroke" => stroke,
0xe1 Nary "fill" => fill,
0xf0 Nary "withDotter" => with_dotter,
}
}
@ -469,7 +544,13 @@ pub mod fns {
fn to_shape(value: Value, vm: &Vm) -> Option<Shape> {
match value {
Value::Nil | Value::False | Value::True | Value::Number(_) | Value::Rgba(_) => None,
Value::Nil
| Value::False
| Value::True
| Value::Tag(_)
| Value::Number(_)
| Value::Rgba(_) => None,
Value::Ref(id) => {
if let Ref::Shape(shape) = vm.get_ref(id) {
Some(shape.clone())
@ -477,6 +558,7 @@ pub mod fns {
None
}
}
Value::Vec4(vec) => Some(Shape::Point(vec.into())),
}
}
@ -588,4 +670,22 @@ pub mod fns {
Ok(Value::Nil)
}
}
pub fn with_dotter(vm: &mut Vm, args: FnArgs) -> Result<Value, Exception> {
if args.num() != 1 {
return Err(vm.create_exception(
"`withDotter` expects a single argument (withDotter \\d -> [])",
));
}
let draw = args.get_closure(vm, 0, "argument to `withDotter` must be a closure")?;
if draw.param_count != 1 {
return Err(vm.create_exception("function passed to `withDotter` must take in a single parameter (withDotter \\d -> [])"));
}
let id = vm.create_ref(Ref::Reticle(Reticle::Dotter {
draw: args.get(vm, 0),
}))?;
Ok(Value::Ref(id))
}
}

78
crates/haku/src/trampoline.rs Normal file
View file

@ -0,0 +1,78 @@
use tiny_skia::Pixmap;
use crate::{
render::{Renderer, RendererLimits},
system::System,
value::{Ref, Reticle, Value, Vec2},
vm::{Exception, Vm},
};
#[derive(Debug, Clone, Copy)]
pub struct Trampoline {
pub value: Value,
}
// NOTE: This must be kept in sync with haku.js.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum Cont {
Scribble,
Dotter,
}
impl Trampoline {
pub fn new(init: Value) -> Self {
Self { value: init }
}
pub fn cont(&self, vm: &Vm) -> Cont {
let Some((_, refv)) = vm.get_ref_value(self.value) else {
return Cont::Scribble;
};
match refv {
Ref::Reticle(_) => Cont::Dotter,
_ => Cont::Scribble,
}
}
pub fn scribble(
&mut self,
vm: &Vm,
pixmap: &mut Pixmap,
translation: Vec2,
limits: &RendererLimits,
) -> Result<(), Exception> {
let mut renderer = Renderer::new(&mut *pixmap, limits);
renderer.translate(translation.x, translation.y);
renderer.render(vm, self.value)
}
pub fn dotter(
&mut self,
vm: &mut Vm,
system: &System,
from: Vec2,
to: Vec2,
num: f32,
) -> Result<(), Exception> {
let (_, vref) = vm.get_ref_value(self.value).expect("value must be a ref");
let &Ref::Reticle(Reticle::Dotter {
draw: Value::Ref(draw_id),
}) = vref
else {
panic!("value must be a dotter reticle");
};
let dotter = vm.create_ref(Ref::Closure(system.create_dotter(
from.into(),
to.into(),
num,
)))?;
let value = vm.run(system, draw_id, &[Value::Ref(dotter)])?;
self.value = value;
Ok(())
}
}

26
crates/haku/src/value.rs
View file

@ -1,6 +1,6 @@
use alloc::vec::Vec;
use crate::{compiler::ClosureSpec, system::ChunkId};
use crate::{bytecode::TagId, compiler::ClosureSpec, system::ChunkId};
// TODO: Probably needs some pretty hardcore space optimization.
// Maybe when we have static typing.
@ -9,6 +9,7 @@ pub enum Value {
Nil,
False,
True,
Tag(TagId),
Number(f32),
Vec4(Vec4),
Rgba(Rgba),
@ -73,6 +74,12 @@ pub struct Vec2 {
pub y: f32,
}
impl Vec2 {
pub fn new(x: f32, y: f32) -> Self {
Self { x, y }
}
}
impl From<Vec4> for Vec2 {
fn from(value: Vec4) -> Self {
Self {
@ -90,6 +97,17 @@ pub struct Vec4 {
pub w: f32,
}
impl From<Vec2> for Vec4 {
fn from(value: Vec2) -> Self {
Self {
x: value.x,
y: value.y,
z: 0.0,
w: 0.0,
}
}
}
#[derive(Debug, Clone, Copy, PartialEq, PartialOrd, Default)]
#[repr(C)]
pub struct Rgba {
@ -123,6 +141,7 @@ pub enum Ref {
List(List),
Shape(Shape),
Scribble(Scribble),
Reticle(Reticle),
}
impl Ref {
@ -206,3 +225,8 @@ pub enum Scribble {
Stroke(Stroke),
Fill(Fill),
}
#[derive(Debug, Clone)]
pub enum Reticle {
Dotter { draw: Value },
}

67
crates/haku/src/vm.rs
View file

@ -5,9 +5,10 @@ use core::{
};
use alloc::{string::String, vec::Vec};
use log::debug;
use crate::{
bytecode::{self, Defs, Opcode, CAPTURE_CAPTURE, CAPTURE_LOCAL},
bytecode::{self, Defs, Opcode, TagId, CAPTURE_CAPTURE, CAPTURE_LOCAL},
system::{ChunkId, System},
value::{BytecodeLoc, Closure, FunctionName, List, Ref, RefId, Rgba, Value, Vec4},
};
@ -178,7 +179,12 @@ impl Vm {
.ok_or_else(|| self.create_exception("corrupted bytecode (call stack underflow)"))
}
pub fn run(&mut self, system: &System, mut closure_id: RefId) -> Result<Value, Exception> {
pub fn run(
&mut self,
system: &System,
mut closure_id: RefId,
params: &[Value],
) -> Result<Value, Exception> {
let closure = self
.get_ref(closure_id)
.as_closure()
@ -191,7 +197,12 @@ impl Vm {
let mut fuel = self.fuel;
let init_bottom = bottom;
for _ in 0..closure.local_count {
let local_count = closure.local_count;
for &param in params {
self.push(param)?;
}
for _ in 0..local_count {
self.push(Value::Nil)?;
}
@ -219,6 +230,11 @@ impl Vm {
Opcode::False => self.push(Value::False)?,
Opcode::True => self.push(Value::True)?,
Opcode::Tag => {
let i = chunk.read_u16(&mut pc)?;
self.push(Value::Tag(TagId::from_u16(i)))?;
}
Opcode::Number => {
let x = chunk.read_f32(&mut pc)?;
self.push(Value::Number(x))?;
@ -344,6 +360,34 @@ impl Vm {
}
}
Opcode::Field => {
let count = chunk.read_u8(&mut pc)? as usize;
let field_tag = self.pop()?;
let Value::Tag(field_tag_id) = field_tag else {
return Err(self.create_exception("name of data field to look up must be a tag (starting with an uppercase letter)"));
};
let mut index = None;
for i in 0..count {
let tag_id = TagId::from_u16(chunk.read_u16(&mut pc)?);
if tag_id == field_tag_id {
index = Some(i);
}
}
let Some(index) = index else {
return Err(self.create_exception(
"field with this name does not exist in the given data structure",
));
};
let closure = self.get_ref(closure_id).as_closure().unwrap();
self.push(closure.captures.get(index).copied().ok_or_else(|| {
self.create_exception("corrupted bytecode (field index out of bounds)")
})?)?;
}
Opcode::Call => {
let argument_count = chunk.read_u8(&mut pc)? as usize;
@ -554,6 +598,23 @@ impl FnArgs {
.to_rgba()
.ok_or_else(|| vm.create_exception(message))
}
#[inline(never)]
pub fn get_closure<'vm>(
&self,
vm: &'vm Vm,
index: usize,
message: &'static str,
) -> Result<&'vm Closure, Exception> {
let value = self.get(vm, index);
let (_, any_ref) = vm
.get_ref_value(value)
.ok_or_else(|| vm.create_exception(message))?;
let Ref::Closure(closure) = any_ref else {
return Err(vm.create_exception(message));
};
Ok(closure)
}
}
#[derive(Debug, Clone, PartialEq, Eq)]

19
crates/haku/tests/language.rs
View file

@ -2,7 +2,7 @@ use std::error::Error;
use haku::{
ast::{dump::dump, Ast},
bytecode::{Chunk, Defs},
bytecode::{Chunk, Defs, DefsLimits},
compiler::{compile_expr, Compiler, Source},
lexer::{lex, Lexer},
parser::{self, Parser, ParserLimits},
@ -14,7 +14,7 @@ use haku::{
};
fn eval(code: &str) -> Result<Value, Box<dyn Error>> {
let mut system = System::new(1);
let mut system = System::new(2);
let code = SourceCode::unlimited_len(code);
@ -32,7 +32,10 @@ fn eval(code: &str) -> Result<Value, Box<dyn Error>> {
system: &system,
};
let mut defs = Defs::new(256);
let mut defs = Defs::new(&DefsLimits {
max_defs: 256,
max_tags: 256,
});
let mut chunk = Chunk::new(65536).unwrap();
let mut compiler = Compiler::new(&mut defs, &mut chunk);
compile_expr(&mut compiler, &src, root)?;
@ -70,7 +73,7 @@ fn eval(code: &str) -> Result<Value, Box<dyn Error>> {
println!("closure spec: {closure_spec:?}");
let closure = vm.create_ref(Ref::Closure(Closure::chunk(chunk_id, closure_spec)))?;
let result = vm.run(&system, closure)?;
let result = vm.run(&system, closure, &[])?;
println!("used fuel: {}", limits.fuel - vm.remaining_fuel());
@ -281,3 +284,11 @@ fn issue_78() {
"#;
assert_eq!(eval(code).unwrap(), Value::Ref(RefId::from_u32(2)))
}
#[test]
fn with_dotter_identity() {
let code = r#"
withDotter \d -> d
"#;
assert_eq!(eval(code).unwrap(), Value::Ref(RefId::from_u32(0)))
}