feat(lisp): rework foreign data system

src/bin/demo.rs

@@ -12,7 +12,6 @@ fn main() {
         "pow",
         "(pow 2 10)",
         "(let '((fib . (lambda (n) (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2))))))) (fib 10))",
-        "(let '((a . (vec3 1 2 3)) (b . (vec3 4 5 6))) (vec3-dot (vec3-norm (vec3-add a b)) a))",
         "(defun do-n-times (f n) (if (= n 0) '() (cons (f) (do-n-times f (- n 1)))))",
         "(do-n-times (lambda () (print 'hello)) 5)",
         "(progn (print 'hello) (print 'world))",

src/lisp/environment.rs

@@ -1,4 +1,4 @@
-use super::{expression::Expression, prelude::mk_prelude, vec::mk_vec3};
+use super::{expression::Expression, prelude::mk_prelude};
 use std::{cell::RefCell, collections::HashMap, rc::Rc};
 
 #[derive(PartialEq, Clone, Debug)]
@@ -124,11 +124,10 @@ impl<'a> Environment<'a> {
 }
 
 impl Default for Environment<'_> {
-    /// Get the default prelude+vec3 layer
+    /// Get the default prelude layer
     fn default() -> Self {
         let mut d = EnvironmentLayer::new();
         mk_prelude(&mut d);
-        mk_vec3(&mut d);
         Environment {
             layer: d,
             outer: None,

src/lisp/eval.rs

@@ -13,6 +13,7 @@ pub enum EvalError {
     ArgumentError(String),
     TypeError(String),
     NotASymbol(Expression),
+    RuntimeError(String),
 }
 
 impl Display for EvalError {
@@ -24,6 +25,7 @@ impl Display for EvalError {
             EvalError::ArgumentError(s) => write!(f, "Argument error: {}", s),
             EvalError::TypeError(s) => write!(f, "Type error: {}", s),
             EvalError::NotASymbol(e) => write!(f, "Expression {} is not a symbol", e),
+            EvalError::RuntimeError(s) => write!(f, "Runtime error: {}", s),
         }
     }
 }

src/lisp/expression.rs

@@ -1,5 +1,8 @@
+use std::any::Any;
 use std::fmt::Debug;
 use std::fmt::Display;
+use std::ops::Deref;
+use std::ops::DerefMut;
 
 use as_any::AsAny;
 
@@ -9,51 +12,110 @@ use super::eval::EvalError;
 
 /// A trait for foreign data types that can be used in lisp expressions.
 /// Note: This trait requires explicit implementation of:
-/// - partial_cmp
-/// - clone_data
-/// - eq
-/// To avoid a derive cycle.
+/// - partial_cmp_impl
+/// - clone_impl
+/// - eq_impl
+/// - as_any_box
+/// to ensure object safety.
 pub trait ForeignData: Debug + Display + AsAny {
-    fn partial_cmp(&self, other: &dyn ForeignData) -> Option<std::cmp::Ordering>;
-    fn clone_data(&self) -> Box<dyn ForeignData>;
-    fn eq(&self, other: &dyn ForeignData) -> bool;
+    fn partial_cmp_impl(&self, other: &dyn ForeignData) -> Option<std::cmp::Ordering>;
+    fn clone_impl(&self) -> Box<dyn ForeignData>;
+    fn eq_impl(&self, other: &dyn ForeignData) -> bool;
+    fn as_any_box(self: Box<Self>) -> Box<dyn Any>;
 }
 
-#[derive(Debug)]
-/// A Wrapper struct for foreign data types injected in expressions.
-pub struct ForeignDataWrapper {
-    /// The actual foreign data.
-    pub data: Box<dyn ForeignData>,
-}
+impl<T: Debug + Display + AsAny + PartialOrd + PartialEq + Clone + 'static> ForeignData for T {
+    fn partial_cmp_impl(&self, other: &dyn ForeignData) -> Option<std::cmp::Ordering> {
+        if let Some(other) = other.as_any().downcast_ref::<T>() {
+            self.partial_cmp(other)
+        } else {
+            None
+        }
+    }
 
-impl ForeignDataWrapper {
-    /// Create a new ForeignDataWrapper from a ForeignData trait object.
-    pub fn new(data: Box<dyn ForeignData>) -> Self {
-        ForeignDataWrapper { data }
+    fn clone_impl(&self) -> Box<dyn ForeignData> {
+        Box::new(self.clone())
+    }
+
+    fn eq_impl(&self, other: &dyn ForeignData) -> bool {
+        if let Some(other) = other.as_any().downcast_ref::<T>() {
+            self.eq(other)
+        } else {
+            false
+        }
+    }
+
+    fn as_any_box(self: Box<Self>) -> Box<dyn Any> {
+        self
     }
 }
 
-impl Clone for ForeignDataWrapper {
+/// A wrapper struct around any foreign data type. This struct is used to convert
+/// any T implementing ForeignData to an Expression and vice versa.
+#[derive(Debug)]
+pub struct ForeignDataWrapper<T: ForeignData>(pub Box<T>);
+impl<T: ForeignData> ForeignDataWrapper<T> {
+    /// Create a new ForeignDataWrapper from an object implementing ForeignData.
+    pub fn new(data: T) -> Self {
+        ForeignDataWrapper(Box::new(data))
+    }
+}
+
+impl<T: ForeignData> Deref for ForeignDataWrapper<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T: ForeignData> DerefMut for ForeignDataWrapper<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+#[derive(Debug)]
+/// A Store struct for foreign data types injected in expressions.
+pub struct ForeignDataStore {
+    /// The actual foreign data.
+    data: Box<dyn ForeignData>,
+}
+
+/// The ForeignDataStore struct is used to store any foreign data type in an Expression
+/// and cannot be constructed outside of this scope.
+impl ForeignDataStore {
+    /// Create a new ForeignDataStore from a ForeignData trait object.
+    fn new(data: Box<dyn ForeignData>) -> Self {
+        ForeignDataStore { data }
+    }
+
+    /// Get the contained box as an Any-Box with type info of the actual data.
+    fn as_any_box(self) -> Box<dyn Any> {
+        self.data.as_any_box()
+    }
+}
+
+impl Clone for ForeignDataStore {
     fn clone(&self) -> Self {
-        ForeignDataWrapper {
-            data: self.data.clone_data(),
+        ForeignDataStore {
+            data: self.data.clone_impl(),
         }
     }
 }
 
-impl PartialEq for ForeignDataWrapper {
+impl PartialEq for ForeignDataStore {
     fn eq(&self, other: &Self) -> bool {
-        self.data.eq(other.data.as_ref())
+        self.data.eq_impl(other.data.as_ref())
     }
 }
 
-impl PartialOrd for ForeignDataWrapper {
+impl PartialOrd for ForeignDataStore {
     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-        self.data.partial_cmp(other.data.as_ref())
+        self.data.partial_cmp_impl(other.data.as_ref())
     }
 }
 
-impl Display for ForeignDataWrapper {
+impl Display for ForeignDataStore {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         write!(f, "{}", self.data)
     }
@@ -72,7 +134,7 @@ pub enum Expression {
         body: Box<Expression>,
     },
     /// A foreign data expression.
-    ForeignExpression(ForeignDataWrapper),
+    ForeignExpression(ForeignDataStore),
     /// A Quoted expression.
     Quote(Box<Expression>),
     /// A symbol.
@@ -89,6 +151,29 @@ pub enum Expression {
     Nil,
 }
 
+impl<T: ForeignData> From<ForeignDataWrapper<T>> for Expression {
+    fn from(value: ForeignDataWrapper<T>) -> Expression {
+        Expression::ForeignExpression(ForeignDataStore::new(value.0))
+    }
+}
+
+impl<T: ForeignData> TryFrom<Expression> for ForeignDataWrapper<T> {
+    type Error = EvalError;
+    fn try_from(value: Expression) -> Result<Self, Self::Error> {
+        match value {
+            Expression::ForeignExpression(f) => match f.as_any_box().downcast::<T>() {
+                Ok(data) => Ok(ForeignDataWrapper(data)),
+                Err(_) => Err(EvalError::TypeError(
+                    "Expression is not a ForeignDataWrapper".to_string(),
+                )),
+            },
+            _ => Err(EvalError::TypeError(
+                "Expression is not a ForeignDataWrapper".to_string(),
+            )),
+        }
+    }
+}
+
 impl From<fn(&Environment, Expression) -> Result<Expression, EvalError>> for Expression {
     fn from(f: fn(&Environment, Expression) -> Result<Expression, EvalError>) -> Self {
         Expression::Function(f)

src/lisp/mod.rs

@@ -2,7 +2,6 @@ pub mod environment;
 pub mod eval;
 pub mod expression;
 pub mod prelude;
-pub mod vec;
 
 pub use environment::Environment;
 pub use eval::eval;

src/lisp/vec.rs

@@ -1,141 +0,0 @@
-use std::fmt::Display;
-
-use super::{
-    environment::{Environment, EnvironmentLayer},
-    eval::{eval, EvalError},
-    expression::ForeignData,
-    expression::{Expression, ForeignDataWrapper},
-};
-
-#[derive(Debug, Clone, Copy)]
-/// A simple 3d vector.
-struct Vec3 {
-    x: f64,
-    y: f64,
-    z: f64,
-}
-
-impl Display for Vec3 {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "(vec3 {} {} {})", self.x, self.y, self.z)
-    }
-}
-
-impl ForeignData for Vec3 {
-    fn clone_data(&self) -> Box<dyn ForeignData> {
-        Box::new(*self)
-    }
-    fn eq(&self, other: &dyn ForeignData) -> bool {
-        if let Some(other) = other.as_any().downcast_ref::<Vec3>() {
-            self.x == other.x && self.y == other.y && self.z == other.z
-        } else {
-            false
-        }
-    }
-    fn partial_cmp(&self, other: &dyn ForeignData) -> Option<std::cmp::Ordering> {
-        if let Some(other) = other.as_any().downcast_ref::<Vec3>() {
-            Some(
-                self.x
-                    .partial_cmp(&other.x)?
-                    .then(self.y.partial_cmp(&other.y)?)
-                    .then(self.z.partial_cmp(&other.z)?),
-            )
-        } else {
-            None
-        }
-    }
-}
-
-impl TryFrom<Expression> for Vec3 {
-    type Error = EvalError;
-    fn try_from(value: Expression) -> Result<Self, Self::Error> {
-        match value {
-            Expression::ForeignExpression(fe) => {
-                if let Some(vec) = fe.data.as_ref().as_any().downcast_ref::<Vec3>() {
-                    Ok(*vec)
-                } else {
-                    Err(EvalError::TypeError("Expected vec3".to_string()))
-                }
-            }
-            _ => Err(EvalError::TypeError("Expected vec3".to_string())),
-        }
-    }
-}
-
-impl From<Vec3> for Expression {
-    fn from(value: Vec3) -> Self {
-        Expression::ForeignExpression(ForeignDataWrapper::new(Box::new(value)))
-    }
-}
-
-/// Create a vec3 expression from a list of 3 floats
-pub fn vec_vec(_env: &Environment, expr: Expression) -> Result<Expression, EvalError> {
-    let [x, y, z]: [f64; 3] = expr.try_into()?;
-
-    Ok(Vec3 { x, y, z }.into())
-}
-
-/// Add two vec3 expressions
-pub fn vec_add(env: &Environment, expr: Expression) -> Result<Expression, EvalError> {
-    let [a, b]: [Expression; 2] = expr.try_into()?;
-
-    let a = Vec3::try_from(eval(env, a)?)?;
-    let b = Vec3::try_from(eval(env, b)?)?;
-
-    Ok(Vec3 {
-        x: a.x + b.x,
-        y: a.y + b.y,
-        z: a.z + b.z,
-    }
-    .into())
-}
-
-/// Scale a vector by a factor. First argument is the factor, second the vector
-pub fn vec_scale(env: &Environment, expr: Expression) -> Result<Expression, EvalError> {
-    let [a, b]: [Expression; 2] = expr.try_into()?;
-
-    let a = f64::try_from(eval(env, a)?)?;
-    let b = Vec3::try_from(eval(env, b)?)?;
-
-    Ok(Vec3 {
-        x: a * b.x,
-        y: a * b.y,
-        z: a * b.z,
-    }
-    .into())
-}
-
-/// Calculate the dot product of two vec3
-pub fn vec_dot(env: &Environment, expr: Expression) -> Result<Expression, EvalError> {
-    let [a, b]: [Expression; 2] = expr.try_into()?;
-
-    let a = Vec3::try_from(eval(env, a)?)?;
-    let b = Vec3::try_from(eval(env, b)?)?;
-
-    Ok(Expression::Float(a.x * b.x + a.y * b.y + a.z * b.z))
-}
-
-/// Get the L2-norm of a vector
-pub fn vec_norm(env: &Environment, expr: Expression) -> Result<Expression, EvalError> {
-    let [arg]: [Expression; 1] = expr.try_into()?;
-
-    let vec = Vec3::try_from(eval(env, arg)?)?;
-
-    let length = (vec.x.powi(2) + vec.y.powi(2) + vec.z.powi(2)).sqrt();
-
-    Ok(Vec3 {
-        x: vec.x / length,
-        y: vec.y / length,
-        z: vec.z / length,
-    }
-    .into())
-}
-
-/// Add vec3 functions to a layer
-pub fn mk_vec3(layer: &mut EnvironmentLayer) {
-    layer.set("vec3".to_string(), Expression::Function(vec_vec));
-    layer.set("vec3-add".to_string(), Expression::Function(vec_add));
-    layer.set("vec3-scale".to_string(), Expression::Function(vec_scale));
-    layer.set("vec3-dot".to_string(), Expression::Function(vec_dot));
-    layer.set("vec3-norm".to_string(), Expression::Function(vec_norm));
-}