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use crate::semantics::{AlphaVar, NzEnv, NzVar, Type, Value};
use crate::syntax::{Label, V};
/// Environment for indexing variables.
#[derive(Debug, Clone, Copy)]
pub(crate) struct VarEnv {
size: usize,
}
/// Environment for resolving names.
#[derive(Debug, Clone)]
pub(crate) struct NameEnv {
names: Vec<Label>,
}
/// Environment for typing expressions.
#[derive(Debug, Clone)]
pub(crate) struct TyEnv {
names: NameEnv,
items: NzEnv,
}
impl VarEnv {
pub fn new() -> Self {
VarEnv { size: 0 }
}
pub fn size(&self) -> usize {
self.size
}
pub fn insert(&self) -> Self {
VarEnv {
size: self.size + 1,
}
}
pub fn lookup(&self, var: &NzVar) -> AlphaVar {
self.lookup_fallible(var).unwrap()
}
pub fn lookup_fallible(&self, var: &NzVar) -> Option<AlphaVar> {
let idx = self.size.checked_sub(var.idx() + 1)?;
Some(AlphaVar::new(idx))
}
}
impl NameEnv {
pub fn new() -> Self {
NameEnv { names: Vec::new() }
}
pub fn as_varenv(&self) -> VarEnv {
VarEnv {
size: self.names.len(),
}
}
pub fn insert(&self, x: &Label) -> Self {
let mut env = self.clone();
env.insert_mut(x);
env
}
pub fn insert_mut(&mut self, x: &Label) {
self.names.push(x.clone())
}
pub fn remove_mut(&mut self) {
self.names.pop();
}
pub fn unlabel_var(&self, var: &V) -> Option<AlphaVar> {
let V(name, idx) = var;
let (idx, _) = self
.names
.iter()
.rev()
.enumerate()
.filter(|(_, n)| *n == name)
.nth(*idx)?;
Some(AlphaVar::new(idx))
}
pub fn label_var(&self, var: &AlphaVar) -> V {
let name = &self.names[self.names.len() - 1 - var.idx()];
let idx = self
.names
.iter()
.rev()
.take(var.idx())
.filter(|n| *n == name)
.count();
V(name.clone(), idx)
}
}
impl TyEnv {
pub fn new() -> Self {
TyEnv {
names: NameEnv::new(),
items: NzEnv::new(),
}
}
pub fn as_varenv(&self) -> VarEnv {
self.names.as_varenv()
}
pub fn as_nzenv(&self) -> &NzEnv {
&self.items
}
pub fn as_nameenv(&self) -> &NameEnv {
&self.names
}
pub fn insert_type(&self, x: &Label, t: Type) -> Self {
TyEnv {
names: self.names.insert(x),
items: self.items.insert_type(t),
}
}
pub fn insert_value(&self, x: &Label, e: Value) -> Self {
TyEnv {
names: self.names.insert(x),
items: self.items.insert_value(e),
}
}
pub fn lookup(&self, var: &V) -> Option<(AlphaVar, Type)> {
let var = self.names.unlabel_var(var)?;
let ty = self.items.lookup_ty(&var);
Some((var, ty))
}
}
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