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use std::{collections::HashMap, rc::Rc};
use intern::Intern;
use self::ast::Lambda;
mod ast;
mod cst;
mod intern;
mod typed;
type SubstTriple = (Intern<ast::Tree>, Intern<ast::Tree>, Intern<ast::Tree>);
#[derive(Debug)]
pub struct Context {
// Abstract tree interning
var_stack: Vec<Rc<ast::Tree>>,
pub tree_interner: intern::TreeInterner,
pub type_interner: intern::TypeInterner,
// Caches
as_tree: HashMap<Intern<cst::Shape>, Rc<ast::Tree>>,
substitute: HashMap<SubstTriple, Option<Rc<ast::Tree>>>,
translate: HashMap<Intern<ast::Tree>, Result<Option<Rc<ast::Tree>>, ast::TranslateError>>,
type_of: HashMap<
Intern<ast::Tree>,
Result<typed::ConstrainedType, typed::TypeError>,
>,
}
impl Context {
/// Converts a concrete syntax tree into an abstract one.
pub fn as_tree(&mut self, shape: &Rc<cst::Shape>) -> Rc<ast::Tree> {
if let Some(tree) = self.as_tree.get(&shape.clone().into()) {
return tree.clone();
}
let tree = cst::as_tree(self, shape);
self.as_tree.insert(shape.clone().into(), tree.clone());
tree
}
/// Creates a copy of `tree` that replaces variables pointing to `from` with `into`.
pub fn substitute(
&mut self,
tree: &Rc<ast::Tree>,
from: &Rc<ast::Tree>,
into: &Rc<ast::Tree>,
) -> Option<Rc<ast::Tree>> {
if let Some(tree) = self.substitute.get(&(
tree.clone().into(),
from.clone().into(),
into.clone().into(),
)) {
return tree.clone();
}
let out = ast::substitute(self, tree, from, into);
self.substitute.insert(
(
tree.clone().into(),
from.clone().into(),
into.clone().into(),
),
out.clone(),
);
out
}
/// Expands let bindings and function calls until the top level construct is a base term.
pub fn translate(
&mut self,
tree: &Rc<ast::Tree>,
) -> Result<Option<Rc<ast::Tree>>, ast::TranslateError> {
if let Some(tree) = self.translate.get(&tree.clone().into()) {
return tree.clone();
}
let out = ast::translate(self, tree);
self.translate.insert(tree.clone().into(), out.clone());
out
}
/// Computes set of unsolvable type constraints for a term. Returns an error
/// if a solvable constraint is unsatisfiable, or the constraints cannot be inferred.
pub fn type_of(
&mut self,
tree: &Rc<ast::Tree>,
) -> Result<typed::ConstrainedType, typed::TypeError> {
if let Some(ty) = self.type_of.get(&tree.clone().into()) {
return ty.clone();
}
let ty = typed::type_of(self, tree);
self.type_of.insert(tree.clone().into(), ty.clone());
ty
}
fn lookup_tree_variable(&self, idx: usize) -> Rc<ast::Tree> {
self.var_stack[idx].clone()
}
fn new_lambda<F: FnOnce(&mut Self) -> Rc<ast::Tree>>(&mut self, f: F) -> Rc<ast::Tree> {
// Create variable node
let arg = Rc::new(ast::Tree::Variable);
// Apply inner with the variable
self.var_stack.push(arg.clone());
let inner = f(self);
self.var_stack.pop();
// Create the lambda
Rc::new(ast::Tree::Lambda(Lambda(arg, inner)))
}
fn new_let<F: FnOnce(&mut Self) -> Rc<ast::Tree>>(
&mut self,
bind: Rc<ast::Tree>,
inner: F,
) -> Rc<ast::Tree> {
// Create variable node
let arg = Rc::new(ast::Tree::Variable);
// Apply inner with the variable
self.var_stack.push(arg.clone());
let inner = inner(self);
self.var_stack.pop();
// Create the let
Rc::new(ast::Tree::Let(bind, arg, inner))
}
}
|
