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Switch out types for evaluator

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This commit is contained in:
greg 2018-08-13 23:28:03 -07:00
parent f9c2fc3f9d
commit 8067c862f3
2 changed files with 108 additions and 77 deletions
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179
schala-lang/src/eval.rs
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@ -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, Clone)]
enum Node {
Expr(Expr),
PrimObject {
name: Rc<String>,
tag: usize,
items: Vec<Node>,
}
}
fn paren_wrapped_vec(terms: impl Iterator<Item=String>) -> String {
let mut buf = String::new();
write!(buf, "(").unwrap();
for term in terms.map(|e| Some(e)).intersperse(None) {
match term {
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*/ Expr,
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::*;
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) {
match term {
Some(e) => write!(buf, "{}", e.to_repl()).unwrap(),
None => write!(buf, ", ").unwrap(),
};
}
write!(buf, ")").unwrap();
buf
}
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) => {
@ -126,79 +148,86 @@ 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 {
literal @ Lit(_) => Ok(literal),
Call { box f, args } => {
match self.expression(f)? {
Constructor { type_name, name, tag, arity} => self.apply_data_constructor(type_name, name, tag, arity, args),
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),
func @ Func(_) => Ok(func),
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 {
Expr::Val(name) => name,
_ => return Err(format!("Trying to assign to a non-value")),
};
match node {
obj @ Node::PrimObject { .. } => Ok(obj),
Node::Expr(expr) => match expr {
literal @ Lit(_) => Ok(Node::Expr(literal)),
Call { box f, args } => {
match self.expression(Node::Expr(f))? {
Node::Expr(Constructor { type_name, name, tag, arity }) => self.apply_data_constructor(type_name, name, tag, arity, 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(Node::Expr(constructor)),
func @ Func(_) => Ok(Node::Expr(func)),
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 {
Expr::Val(name) => name,
_ => return Err(format!("Trying to assign to a non-value")),
};
let constant = match self.values.lookup(&name) {
None => return Err(format!("{} is undefined", name)),
Some(ValueEntry::Binding { constant, .. }) => constant.clone(),
};
if constant {
return Err(format!("trying to update {}, a non-mutable binding", name));
}
let val = self.expression(expr)?;
self.values.insert(name.clone(), ValueEntry::Binding { constant: false, val });
Ok(Expr::Unit)
},
e => Err(format!("Expr {:?} eval not implemented", e))
let constant = match self.values.lookup(&name) {
None => return Err(format!("{} is undefined", name)),
Some(ValueEntry::Binding { constant, .. }) => constant.clone(),
};
if constant {
return Err(format!("trying to update {}, a non-mutable binding", name));
}
let val = self.expression(Node::Expr(expr))?;
self.values.insert(name.clone(), ValueEntry::Binding { constant: false, val });
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> {
let cond = self.expression(cond)?;
fn conditional(&mut self, cond: Expr, then_clause: Vec<Stmt>, else_clause: Vec<Stmt>) -> EvalResult<Node> {
let cond = self.expression(Node::Expr(cond))?;
Ok(match cond {
Expr::Lit(Lit::Bool(true)) => self.block(then_clause)?,
Expr::Lit(Lit::Bool(false)) => self.block(else_clause)?,
Node::Expr(Expr::Lit(Lit::Bool(true))) => self.block(then_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 }), .. }) => {
Expr::Func(UserDefined { name: name.clone(), params: params.clone(), body: body.clone() })
Some(Binding { val: Node::Expr(Expr::Func(UserDefined { name, params, body })), .. }) => {
Node::Expr(Expr::Func(UserDefined { name: name.clone(), params: params.clone(), body: body.clone() }))
},
_ => unreachable!(),
},

6
schala-lang/src/reduced_ast.rs
View File

@ -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)]
@ -156,7 +152,7 @@ fn reduce_if_expression(discriminator: &Discriminator, body: &IfExpressionBody,
None => vec![],
Some(stmts) => stmts.iter().map(|expr| expr.reduce(symbol_table)).collect(),
};
let first_alt: Alternative = match pat {
Pattern::TupleStruct(name, subpatterns) => {
let symbol = symbol_table.values.get(name).unwrap();