rename

Cargo.lock

@@ -1416,18 +1416,18 @@ dependencies = [
 
 [[package]]
 name = "thiserror"
-version = "1.0.31"
+version = "1.0.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bd829fe32373d27f76265620b5309d0340cb8550f523c1dda251d6298069069a"
+checksum = "f5f6586b7f764adc0231f4c79be7b920e766bb2f3e51b3661cdb263828f19994"
 dependencies = [
  "thiserror-impl",
 ]
 
 [[package]]
 name = "thiserror-impl"
-version = "1.0.31"
+version = "1.0.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0396bc89e626244658bef819e22d0cc459e795a5ebe878e6ec336d1674a8d79a"
+checksum = "12bafc5b54507e0149cdf1b145a5d80ab80a90bcd9275df43d4fff68460f6c21"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1738,6 +1738,7 @@ dependencies = [
  "logos",
  "ordered-float",
  "rustyline",
+ "thiserror",
 ]
 
 [[package]]

Cargo.toml

@@ -12,3 +12,4 @@ eframe = "*"
 logos = "*"
 ordered-float = "3.0"
 rustyline = "10.0"
+thiserror = "1.0"

src/error.rs

@@ -1,10 +1,11 @@
 use crate::syntax::lexer::Token;
 use ariadne::{Color, Fmt, Label, Report, ReportKind, Source};
 use chumsky::error::{Simple, SimpleReason};
-use std::fmt::Display;
+use thiserror::Error;
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Error, Clone)]
 pub enum Error<'a> {
+    #[error("parse error: {0:?}")]
     Parse(Simple<Token<'a>>),
 }
 
@@ -73,13 +74,3 @@ impl<'a> Error<'a> {
         }
     }
 }
-
-impl<'a> Display for Error<'a> {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Error::Parse(e) => write!(f, "{e:?}"),
-        }
-    }
-}
-
-impl<'a> std::error::Error for Error<'a> {}

src/interpreter/bytecode.rs

@@ -0,0 +1,28 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Instruction {
+    /// Call a function on top of the stack
+    /// with n arguments
+    Call(usize),
+
+    /// Unconditional jump by offset
+    Jump(isize),
+
+    /// Jump by offset if value on
+    /// top of the stack is falsey (nil)
+    JumpN(isize),
+
+    /// Load a value from constants table
+    LdConst(usize),
+
+    /// Load a value from locals table
+    LdLocal(usize),
+
+    /// Store a value to locals table
+    StLocal(usize),
+
+    /// Drop a value from stack
+    Drop,
+
+    /// Duplicate value on stack
+    Dup,
+}

src/interpreter/context.rs

@@ -0,0 +1,159 @@
+//! Evaluation context for Wisp
+
+use super::{
+    bytecode::Instruction,
+    value::{Function, Value},
+};
+use crate::interpreter::value::NativeFun;
+use std::rc::Rc;
+use thiserror::Error;
+
+type Result<T, E = Error> = std::result::Result<T, E>;
+
+pub struct Context<'s> {
+    fun: Rc<Function<'s>>,
+    stack: Vec<Value<'s>>,
+    locals: Vec<Value<'s>>,
+    pc: usize,
+}
+
+impl<'s> Context<'s> {
+    /// Create a new evaluation context
+    pub fn new(fun: Rc<Function<'s>>) -> Self {
+        Self {
+            stack: vec![],
+            locals: vec![Value::Nil; fun.locals_len],
+            pc: 0,
+            fun,
+        }
+    }
+
+    /// Execute whole function and return last value on stack (or nil)
+    pub fn execute(&mut self) -> Result<Value<'s>> {
+        let len = self.fun.bytecode.len();
+        while self.pc < len {
+            self.tick()?;
+        }
+
+        Ok(self.stack.pop().unwrap_or(Value::Nil))
+    }
+
+    /// Execute next instruction
+    pub fn tick(&mut self) -> Result<()> {
+        use Instruction::*;
+        match self
+            .fun
+            .bytecode
+            .get(self.pc)
+            .copied()
+            .ok_or(IndexOutOfBoundsError::Bytecode)?
+        {
+            Call(n) if n >= self.stack.len() => return Err(IndexOutOfBoundsError::Stack.into()),
+            Call(n) => {
+                let fun = self.stack_pop()?;
+                let mut args = self.stack.split_off(self.stack.len() - n);
+                match fun {
+                    Value::Function(fun) => {
+                        if fun.locals_len > args.len() {
+                            args.resize(fun.locals_len, Value::Nil);
+                        }
+
+                        self.stack.push(
+                            Context {
+                                stack: vec![],
+                                locals: args,
+                                pc: 0,
+                                fun,
+                            }
+                            .execute()?,
+                        );
+                    }
+                    Value::NativeFun(NativeFun(f)) => {
+                        let v = f(&args);
+                        self.stack.push(v);
+                    }
+                    _ => unimplemented!("invalid function type"),
+                }
+            }
+            Jump(o) => {
+                self.jump(o);
+                return Ok(());
+            }
+            JumpN(o) => {
+                if self.stack_pop()? == Value::Nil {
+                    self.jump(o);
+                    return Ok(());
+                }
+            }
+            LdConst(i) => {
+                self.stack.push(
+                    self.fun
+                        .consts
+                        .get(i)
+                        .cloned()
+                        .ok_or(IndexOutOfBoundsError::Const)?,
+                );
+            }
+            LdLocal(i) => {
+                self.stack.push(
+                    self.locals
+                        .get(i)
+                        .cloned()
+                        .ok_or(IndexOutOfBoundsError::Local)?,
+                );
+            }
+            StLocal(i) => {
+                *self.locals.get_mut(i).ok_or(IndexOutOfBoundsError::Local)? = self.stack_pop()?;
+            }
+            Drop => {
+                self.stack_pop()?;
+            }
+            Dup => {
+                self.stack.push(
+                    self.stack
+                        .last()
+                        .cloned()
+                        .ok_or(IndexOutOfBoundsError::Stack)?,
+                );
+            }
+        }
+
+        self.pc += 1;
+        Ok(())
+    }
+
+    /// Jump by offset
+    fn jump(&mut self, offset: isize) {
+        (if offset.is_negative() {
+            std::ops::SubAssign::sub_assign
+        } else {
+            std::ops::AddAssign::add_assign
+        })(&mut self.pc, offset.unsigned_abs());
+    }
+
+    /// Pop a value from a stack
+    fn stack_pop(&mut self) -> Result<Value<'s>, IndexOutOfBoundsError> {
+        self.stack.pop().ok_or(IndexOutOfBoundsError::Stack)
+    }
+}
+
+#[derive(Debug, Clone, Error)]
+pub enum Error {
+    #[error(transparent)]
+    IndexOutOfBounds(#[from] IndexOutOfBoundsError),
+}
+
+#[derive(Debug, Clone, Error)]
+pub enum IndexOutOfBoundsError {
+    #[error("bytecode index out of bounds")]
+    Bytecode,
+
+    #[error("const index out of bounds")]
+    Const,
+
+    #[error("stack index out of bounds")]
+    Stack,
+
+    #[error("locals index out of bounds")]
+    Local,
+}

src/interpreter/mod.rs

@@ -0,0 +1,12 @@
+//! **bodge**
+//! (third-person singular simple present bodges, present participle **bodging**,
+//! simple past and past participle **bodged**)
+//! 1. (Britain) To do a clumsy or inelegant job, usually as a temporary repair; mend, patch up, repair.
+//! 2. To work green wood using traditional country methods; to perform the craft of a bodger.
+//!
+//! A simple silly compiler + VM intended for testing purposes.
+//! To be replaced by something better soon™️ :ferrisClueless:
+
+pub mod bytecode;
+pub mod context;
+pub mod value;

src/interpreter/value/function.rs

@@ -0,0 +1,29 @@
+use std::fmt::Debug;
+
+use super::Value;
+use crate::interpreter::bytecode::Instruction;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Function<'s> {
+    pub bytecode: Box<[Instruction]>,
+    pub consts: Box<[Value<'s>]>,
+    pub locals_len: usize,
+}
+
+#[derive(Clone)]
+pub struct NativeFun<'s>(pub fn(&[Value<'s>]) -> Value<'s>);
+impl<'s> Debug for NativeFun<'s> {
+    fn fmt<'a>(&'a self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_tuple("NativeFun")
+            .field(&(self.0 as fn(&'a _) -> _))
+            .finish()
+    }
+}
+
+impl<'s> PartialEq for NativeFun<'s> {
+    fn eq<'a>(&'a self, other: &Self) -> bool {
+        (self.0 as fn(&'a _) -> _) == other.0
+    }
+}
+
+impl<'s> Eq for NativeFun<'s> {}

src/interpreter/value/mod.rs

@@ -0,0 +1,92 @@
+mod function;
+mod pair;
+mod string;
+
+pub use function::{Function, NativeFun};
+pub use pair::DotPair;
+pub use string::Str;
+
+use crate::syntax::ast::{Expr, Spanned};
+use pair::list;
+use std::{collections::BTreeMap, fmt::Display, rc::Rc};
+
+pub type OrderedF64 = ordered_float::OrderedFloat<f64>;
+
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+pub enum Value<'s> {
+    #[default]
+    Nil,
+    DotPair(DotPair<'s>),
+    Vector(Rc<Vec<Self>>),
+    Map(Rc<BTreeMap<Self, Self>>),
+    Symbol(Str<'s>),
+    Keyword(Str<'s>),
+    Number(OrderedF64),
+    String(Str<'s>),
+    Function(Rc<Function<'s>>),
+    NativeFun(NativeFun<'s>),
+    Macro(Rc<Function<'s>>),
+}
+
+impl<'s> From<Spanned<Expr<'s>>> for Value<'s> {
+    fn from(e: Spanned<Expr<'s>>) -> Self {
+        e.item.into()
+    }
+}
+
+impl<'s> From<Expr<'s>> for Value<'s> {
+    fn from(e: Expr<'s>) -> Self {
+        match e {
+            Expr::List(v) => v.into_iter().rev().fold(Self::Nil, |acc, x| {
+                Value::DotPair(DotPair::new(x.into(), acc))
+            }),
+            Expr::Vector(v) => Self::Vector(Rc::new(v.into_iter().map(Into::into).collect())),
+            Expr::Pair((l, r)) => Self::DotPair(DotPair::new((*l).into(), (*r).into())),
+            Expr::Quote(e) => list!(Self::Symbol("quote".into()), (*e).into()),
+            Expr::Symbol("nil") => Self::Nil,
+            Expr::Symbol(s) => Self::Symbol(s.into()),
+            Expr::Keyword(s) => Self::Keyword(s.into()),
+            Expr::Number(n) => Self::Number(n),
+            Expr::String(s) => Self::String(s.into()),
+        }
+    }
+}
+
+impl<'s> Display for Value<'s> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Value::Nil => "nil".fmt(f),
+            Value::DotPair(p) => p.fmt(f),
+            Value::Vector(v) => fmt_sequence(f, v.as_ref(), "#(", ")", |i, f| i.fmt(f)),
+            Value::Map(m) => {
+                fmt_sequence(f, m.as_ref(), "(", ")", |(k, v), f| write!(f, "{k} -> {v}"))
+            }
+            Value::Symbol(s) => s.fmt(f),
+            Value::Keyword(k) => write!(f, ":{k}"),
+            Value::Number(n) => n.fmt(f),
+            Value::String(s) => write!(f, "\"{s}\""),
+            Value::Function(_) => "#fun#".fmt(f),
+            Value::NativeFun(fp) => write!(f, "#native-fun({fp:p})#"),
+            Value::Macro(_) => "#macro#".fmt(f),
+        }
+    }
+}
+
+fn fmt_sequence<T>(
+    f: &mut std::fmt::Formatter<'_>,
+    s: impl IntoIterator<Item = T>,
+    start: &str,
+    end: &str,
+    it_fmt: impl Fn(T, &mut std::fmt::Formatter<'_>) -> std::fmt::Result,
+) -> std::fmt::Result {
+    let mut it = s.into_iter();
+    start.fmt(f)?;
+    if let Some(i) = it.next() {
+        it_fmt(i, f)?;
+    }
+    for i in it {
+        " ".fmt(f)?;
+        it_fmt(i, f)?;
+    }
+    end.fmt(f)
+}

src/interpreter/value/pair.rs

@@ -0,0 +1,60 @@
+use super::Value;
+use std::{fmt::Display, rc::Rc};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct DotPair<'s>(pub Rc<(Value<'s>, Value<'s>)>);
+impl<'s> DotPair<'s> {
+    pub fn new(first: Value<'s>, second: Value<'s>) -> Self {
+        Self(Rc::new((first, second)))
+    }
+
+    pub fn first(&self) -> &Value<'s> {
+        &self.0 .0
+    }
+
+    pub fn second(&self) -> &Value<'s> {
+        &self.0 .1
+    }
+}
+
+impl<'s> Display for DotPair<'s> {
+    fn fmt(mut self: &Self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        "(".fmt(f)?;
+        loop {
+            self.first().fmt(f)?;
+            match self.second() {
+                Value::Nil => break,
+                Value::DotPair(p) => {
+                    " ".fmt(f)?;
+                    self = p;
+                }
+                val => break write!(f, " . {val}")?,
+            }
+        }
+        ")".fmt(f)?;
+        Ok(())
+    }
+}
+
+macro_rules! list {
+    () => {
+        $crate::interpreter::value::Value::Nil
+    };
+
+    ($item: expr $(,)?) => {
+        Value::DotPair(
+            $crate::interpreter::value::DotPair::new($item, $crate::interpreter::value::Value::Nil)
+        )
+    };
+
+    ($first: expr, $($rest: expr),* $(,)?) => {
+        Value::DotPair(
+            $crate::interpreter::value::DotPair::new(
+                $first,
+                $crate::interpreter::value::pair::list!($($rest),*)
+            )
+        )
+    };
+}
+
+pub(crate) use list;

src/interpreter/value/string.rs

@@ -0,0 +1,57 @@
+use std::{fmt::Display, hash::Hash, ops::Deref, rc::Rc};
+
+/// A Wisp string type which can hold two variants:
+/// - Borrowed (usually a reference to source code or built-in literal)
+/// - Shared (Ref-counted pointer to [`str`])
+#[derive(Debug, Clone)]
+pub enum Str<'a> {
+    Borrowed(&'a str),
+    Shared(Rc<str>),
+}
+
+impl<'a> From<&'a str> for Str<'a> {
+    fn from(x: &'a str) -> Self {
+        Self::Borrowed(x)
+    }
+}
+
+impl<'a> From<Rc<str>> for Str<'a> {
+    fn from(x: Rc<str>) -> Self {
+        Self::Shared(x)
+    }
+}
+
+impl<'a> Deref for Str<'a> {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            Self::Borrowed(b) => b,
+            Self::Shared(s) => s,
+        }
+    }
+}
+
+impl<'a> PartialEq for Str<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        **self == **other
+    }
+}
+
+impl<'a> Eq for Str<'a> {}
+
+impl<'a> Hash for Str<'a> {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        (**self).hash(state);
+    }
+}
+
+impl<'a> Display for Str<'a> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Str::Borrowed(b) => *b,
+            Str::Shared(s) => s,
+        }
+        .fmt(f)
+    }
+}

src/lib.rs

@@ -1,3 +1,4 @@
 pub mod error;
+pub mod interpreter;
 pub mod repl;
 pub mod syntax;

src/repl.rs

@@ -1,4 +1,4 @@
-use crate::{error::Error, syntax::parser::parse};
+use crate::{error::Error, interpreter::value::Value, syntax::parser::parse};
 use rustyline::{error::ReadlineError, Editor};
 
 pub fn repl() -> rustyline::Result<()> {
@@ -7,7 +7,9 @@ pub fn repl() -> rustyline::Result<()> {
     loop {
         match rl.readline(prompt) {
             Ok(line) => match parse(&line) {
-                Ok(values) => values.iter().for_each(|e| println!("{e}")),
+                Ok(values) => values
+                    .into_iter()
+                    .for_each(|e| println!("{}", Into::<Value>::into(e))),
                 Err(e) => e.into_iter().map(Error::Parse).for_each(|e| {
                     if let Err(e) = e.report(&line) {
                         eprintln!("Failed to generate error report\n{e:?}")

src/syntax/ast.rs

@@ -31,6 +31,8 @@ impl<T: PartialEq> PartialEq for Spanned<T> {
     }
 }
 
+impl<T: Eq> Eq for Spanned<T> {}
+
 impl<T: Hash> Hash for Spanned<T> {
     fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
         self.item.hash(state);
@@ -38,7 +40,7 @@ impl<T: Hash> Hash for Spanned<T> {
 }
 
 /// A Wisp AST
-#[derive(Debug, Clone, Hash, PartialEq)]
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub enum Expr<'s> {
     List(Vec<Spanned<Self>>),
     Vector(Vec<Spanned<Self>>),

src/syntax/parser.rs

@@ -33,24 +33,22 @@ fn parser<'s>() -> impl Parser<Token<'s>, Vec<Spanned<Expr<'s>>>, Error = Simple
         let list = list.map(Expr::List);
 
         let quote = just(Token::Quote)
-            .ignore_then(expr)
+            .ignore_then(expr.clone())
             .map(Box::new)
             .map(Expr::Quote);
 
-        let without_pair = atom
+        let pair = expr
+            .clone()
+            .then_ignore(just(Token::Dot))
+            .then(expr)
+            .delimited_by(just(Token::LeftParen), just(Token::RightParen))
+            .map(|(l, r)| Expr::Pair((Box::new(l), Box::new(r))));
+
+        atom.or(pair)
             .or(list)
             .or(vector)
             .or(quote)
-            .map_with_span(Spanned::new);
+            .map_with_span(Spanned::new)
-
-        let pair = without_pair
-            .clone()
-            .then_ignore(just(Token::Dot))
-            .then(without_pair.clone())
-            .map(|(l, r)| Expr::Pair((Box::new(l), Box::new(r))))
-            .map_with_span(Spanned::new);
-
-        pair.or(without_pair)
     })
     .repeated()
     .then_ignore(end())