Switch out types for evaluator

schala-lang/src/eval.rs

@@ -16,7 +16,7 @@ pub struct State<'a> {
 
 macro_rules! builtin_binding {
   ($name:expr, $values:expr) => {
-    $values.insert(Rc::new(format!($name)), ValueEntry::Binding { constant: true, val: Expr::Func(Func::BuiltIn(Rc::new(format!($name)))) });
+    $values.insert(Rc::new(format!($name)), ValueEntry::Binding { constant: true, val: Node::Expr(Expr::Func(Func::BuiltIn(Rc::new(format!($name))))) });
   }
 }
 
@@ -34,33 +34,57 @@ impl<'a> State<'a> {
   }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
-enum ValueEntry {
+enum Node {
-  Binding {
+  Expr(Expr),
-    constant: bool,
+  PrimObject {
-    val: /*FullyEvaluatedExpr*/ Expr,
+    name: Rc<String>,
+    tag: usize,
+    items: Vec<Node>,
   }
 }
 
-type EvalResult<T> = Result<T, String>;
+fn paren_wrapped_vec(terms: impl Iterator<Item=String>) -> String {
-
-
-impl Expr {
-  fn to_repl(&self) -> String {
-    use self::Lit::*;
-    use self::Func::*;
-    fn paren_wrapped_vec(exprs: &Vec<Expr>) -> String {
   let mut buf = String::new();
   write!(buf, "(").unwrap();
-      for term in exprs.iter().map(|e| Some(e)).intersperse(None) {
+  for term in terms.map(|e| Some(e)).intersperse(None) {
     match term {
-          Some(e) => write!(buf, "{}", e.to_repl()).unwrap(),
+      Some(e) => write!(buf, "{}", e).unwrap(),
       None => write!(buf, ", ").unwrap(),
     };
   }
   write!(buf, ")").unwrap();
   buf
+}
+
+
+impl Node {
+  fn to_repl(&self) -> String {
+    match self {
+      Node::Expr(e) => e.to_repl(),
+      Node::PrimObject { name, items, tag } if items.len() == 0 => format!("{}", name),
+      Node::PrimObject { name, items, tag } => format!("{}{}", name, paren_wrapped_vec(items.iter().map(|x| x.to_repl()))),
     }
+  }
+}
+
+#[derive(Debug)]
+enum ValueEntry {
+  Binding {
+    constant: bool,
+    val: /*FullyEvaluatedExpr*/ Node, //TODO make this use a subtype to represent fully evaluatedness
+  }
+}
+
+type EvalResult<T> = Result<T, String>;
+
+impl Expr {
+  fn to_node(self) -> Node {
+    Node::Expr(self)
+  }
+  fn to_repl(&self) -> String {
+    use self::Lit::*;
+    use self::Func::*;
 
     match self {
       Expr::Lit(ref l) => match l {
@@ -69,8 +93,6 @@ impl Expr {
         Float(f) => format!("{}", f),
         Bool(b) => format!("{}", b),
         StringLit(s) => format!("\"{}\"", s),
-        PrimObject { name, items } if items.len() == 0 => format!("{}", name),
-        PrimObject { name, items } => format!("{}{}", name, paren_wrapped_vec(items)),
       },
       Expr::Func(f) => match f {
         BuiltIn(name) => format!("<built-in function '{}'>", name),
@@ -84,7 +106,7 @@ impl Expr {
       } else {
         format!("<data constructor '{}'>", name)
       },
-      Expr::Tuple(exprs) => paren_wrapped_vec(exprs),
+      Expr::Tuple(exprs) => paren_wrapped_vec(exprs.iter().map(|x| x.to_repl())),
       _ => format!("{:?}", self),
     }
   }
@@ -115,7 +137,7 @@ impl<'a> State<'a> {
   fn prebinding(&mut self, stmt: &Stmt) {
     match stmt {
       Stmt::PreBinding { name, func } => {
-        let v_entry = ValueEntry::Binding { constant: true, val: Expr::Func(func.clone()) };
+        let v_entry = ValueEntry::Binding { constant: true, val: Node::Expr(Expr::Func(func.clone())) };
         self.values.insert(name.clone(), v_entry);
       },
       Stmt::Expr(_expr) => {
@@ -126,41 +148,46 @@ impl<'a> State<'a> {
     }
   }
 
-  fn statement(&mut self, stmt: Stmt) -> EvalResult<Option<Expr>> {
+  fn statement(&mut self, stmt: Stmt) -> EvalResult<Option<Node>> {
     match stmt {
       Stmt::Binding { name, constant, expr } => {
-        let val = self.expression(expr)?;
+        let val = self.expression(Node::Expr(expr))?;
         self.values.insert(name.clone(), ValueEntry::Binding { constant, val });
         Ok(None)
       },
-      Stmt::Expr(expr) => Ok(Some(self.expression(expr)?)),
+      Stmt::Expr(expr) => Ok(Some(self.expression(expr.to_node())?)),
       Stmt::PreBinding {..} | Stmt::Noop => Ok(None),
     }
   }
 
-  fn block(&mut self, stmts: Vec<Stmt>) -> EvalResult<Expr> {
+  fn block(&mut self, stmts: Vec<Stmt>) -> EvalResult<Node> {
     let mut ret = None;
     for stmt in stmts {
       ret = self.statement(stmt)?;
     }
-    Ok(ret.unwrap_or(Expr::Unit))
+    Ok(ret.unwrap_or(Node::Expr(Expr::Unit)))
   }
 
-  fn expression(&mut self, expr: Expr) -> EvalResult<Expr> {
+  fn expression(&mut self, node: Node) -> EvalResult<Node> {
     use self::Expr::*;
-    match expr {
+    match node {
-      literal @ Lit(_) => Ok(literal),
+      obj @ Node::PrimObject { .. } =>  Ok(obj),
+      Node::Expr(expr) => match expr {
+        literal @ Lit(_) => Ok(Node::Expr(literal)),
         Call { box f, args } => {
-        match self.expression(f)? {
+          match self.expression(Node::Expr(f))? {
-          Constructor { type_name, name, tag, arity} => self.apply_data_constructor(type_name, name, tag, arity, args),
+            Node::Expr(Constructor { type_name, name, tag, arity }) => self.apply_data_constructor(type_name, name, tag, arity, args),
-          Func(f) => self.apply_function(f, args),
+            Node::Expr(Func(f)) => self.apply_function(f, args),
             other => return Err(format!("Tried to call {:?} which is not a function or data constructor", other)),
           }
         },
         Val(v) => self.value(v),
-      constructor @ Constructor { .. } => Ok(constructor),
+        constructor @ Constructor { .. } => Ok(Node::Expr(constructor)),
-      func @ Func(_) => Ok(func),
+        func @ Func(_) => Ok(Node::Expr(func)),
-      Tuple(exprs) => Ok(Tuple(exprs.into_iter().map(|expr| self.expression(expr)).collect::<Result<Vec<Expr>,_>>()?)),
+        Tuple(exprs) => {
+          unimplemented!()
+        },
+        //Tuple(exprs) => Ok(Tuple(exprs.into_iter().map(|expr| self.expression(expr)).collect::<Result<Vec<Expr>,_>>()?)),
         Conditional { box cond, then_clause, else_clause } => self.conditional(cond, then_clause, else_clause),
         Assign { box val, box expr } => {
           let name = match val  {
@@ -175,30 +202,32 @@ impl<'a> State<'a> {
           if constant {
             return Err(format!("trying to update {}, a non-mutable binding", name));
           }
-        let val = self.expression(expr)?;
+          let val = self.expression(Node::Expr(expr))?;
           self.values.insert(name.clone(), ValueEntry::Binding { constant: false, val });
-        Ok(Expr::Unit)
+          Ok(Node::Expr(Expr::Unit))
         },
         e => Err(format!("Expr {:?} eval not implemented", e))
       }
     }
+  }
 
-  fn apply_data_constructor(&mut self, type_name: Rc<String>, name: Rc<String>, tag: usize, arity: usize, args: Vec<Expr>) -> EvalResult<Expr> {
+  fn apply_data_constructor(&mut self, type_name: Rc<String>, name: Rc<String>, tag: usize, arity: usize, args: Vec<Expr>) -> EvalResult<Node> {
     if arity != args.len() {
       return Err(format!("Data constructor {} requires {} args", name, arity));
     }
 
-    let evaled_args = args.into_iter().map(|expr| self.expression(expr)).collect::<Result<Vec<Expr>,_>>()?;
+    let evaled_args = args.into_iter().map(|expr| self.expression(Node::Expr(expr))).collect::<Result<Vec<Node>,_>>()?;
     //let evaled_args = vec![];
-    Ok(Expr::Lit(self::Lit::PrimObject {
+    Ok(Node::PrimObject {
       name: name.clone(),
       items: evaled_args,
-    }))
+      tag: 0,
+    })
   }
 
-  fn apply_function(&mut self, f: Func, args: Vec<Expr>) -> EvalResult<Expr> {
+  fn apply_function(&mut self, f: Func, args: Vec<Expr>) -> EvalResult<Node> {
     match f {
-      Func::BuiltIn(sigil) => self.apply_builtin(sigil, args),
+      Func::BuiltIn(sigil) => Ok(Node::Expr(self.apply_builtin(sigil, args)?)),
       Func::UserDefined { params, body, name } => {
 
         if params.len() != args.len() {
@@ -209,7 +238,7 @@ impl<'a> State<'a> {
           symbol_table_handle: self.symbol_table_handle.clone(),
         };
         for (param, val) in params.into_iter().zip(args.into_iter()) {
-          let val = func_state.expression(val)?;
+          let val = func_state.expression(Node::Expr(val))?;
           func_state.values.insert(param, ValueEntry::Binding { constant: true, val });
         }
         // TODO figure out function return semantics
@@ -221,7 +250,13 @@ impl<'a> State<'a> {
   fn apply_builtin(&mut self, name: Rc<String>, args: Vec<Expr>) -> EvalResult<Expr> {
     use self::Expr::*;
     use self::Lit::*;
-    let evaled_args: Result<Vec<Expr>, String> = args.into_iter().map(|arg| self.expression(arg)).collect();
+    let evaled_args: Result<Vec<Expr>, String> = args.into_iter().map(|arg| {
+      match self.expression(Node::Expr(arg)) {
+        Ok(Node::Expr(e)) => Ok(e),
+        Ok(Node::PrimObject { .. }) => Err(format!("Trying to apply a builtin to a primitive object")),
+        Err(e) => Err(e)
+      }
+    }).collect();
     let evaled_args = evaled_args?;
 
     Ok(match (name.as_str(), evaled_args.as_slice()) {
@@ -274,16 +309,16 @@ impl<'a> State<'a> {
     })
   }
 
-  fn conditional(&mut self, cond: Expr, then_clause: Vec<Stmt>, else_clause: Vec<Stmt>) -> EvalResult<Expr> {
+  fn conditional(&mut self, cond: Expr, then_clause: Vec<Stmt>, else_clause: Vec<Stmt>) -> EvalResult<Node> {
-    let cond = self.expression(cond)?;
+    let cond = self.expression(Node::Expr(cond))?;
     Ok(match cond {
-      Expr::Lit(Lit::Bool(true)) =>  self.block(then_clause)?,
+      Node::Expr(Expr::Lit(Lit::Bool(true))) =>  self.block(then_clause)?,
-      Expr::Lit(Lit::Bool(false)) => self.block(else_clause)?,
+      Node::Expr(Expr::Lit(Lit::Bool(false))) => self.block(else_clause)?,
       _ => return Err(format!("Conditional with non-boolean condition"))
     })
   }
 
-  fn value(&mut self, name: Rc<String>) -> EvalResult<Expr> {
+  fn value(&mut self, name: Rc<String>) -> EvalResult<Node> {
     use self::ValueEntry::*;
     use self::Func::*;
     //TODO add a layer of indirection here to talk to the symbol table first, and only then look up
@@ -295,14 +330,14 @@ impl<'a> State<'a> {
       Some(Symbol { name, spec }) => match spec {
         SymbolSpec::DataConstructor { type_name, type_args, .. } => {
           if type_args.len() == 0 {
-            Expr::Lit(Lit::PrimObject { name: name.clone(), items: vec![] })
+            Node::PrimObject { name: name.clone(), tag: 0, items: vec![] }
           } else {
             return Err(format!("This data constructor thing not done"))
           }
         },
         SymbolSpec::Func(_) => match self.values.lookup(&name) {
-          Some(Binding { val: Expr::Func(UserDefined { name, params, body }), .. }) => {
+          Some(Binding { val: Node::Expr(Expr::Func(UserDefined { name, params, body })), .. }) => {
-            Expr::Func(UserDefined { name: name.clone(), params: params.clone(), body: body.clone() })
+            Node::Expr(Expr::Func(UserDefined { name: name.clone(), params: params.clone(), body: body.clone() }))
           },
           _ => unreachable!(),
         },

schala-lang/src/reduced_ast.rs

@@ -69,10 +69,6 @@ pub enum Lit {
   Float(f64),
   Bool(bool),
   StringLit(Rc<String>),
-  PrimObject { //TODO rethink placement in type heierarchy
-    name: Rc<String>,
-    items: Vec<Expr>,
-  }
 }
 
 #[derive(Debug, Clone)]