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authorNadrieril2019-04-20 01:55:21 +0200
committerNadrieril2019-04-20 10:45:12 +0200
commit151a14dad84d4d0f02045ea9b69d63e2cb9fe17e (patch)
treec9b954244bc335f9150757ea321a588a7393c6d4 /dhall
parent19b74fb2f0d2f69d304e14d9d3419947348c0de0 (diff)
Improve WHNF ergonomics
This will be needed for the apply_builtin rewrite anyways
Diffstat (limited to '')
-rw-r--r--dhall/src/normalize.rs239
1 files changed, 135 insertions, 104 deletions
diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index e88cc7b..b038efd 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -208,22 +208,22 @@ fn apply_builtin(b: Builtin, args: &[WHNF]) -> WhatNext<X, X> {
/// this means knowing just the field names.
///
/// Each variant captures the relevant contexts when it is constructed. Conceptually each
-/// subexpression has its own context, but in practise contexts can be shared when sensible, to
+/// subexpression has its own context, but in practice some contexts can be shared when sensible, to
/// avoid unnecessary allocations.
#[derive(Debug, Clone)]
enum WHNF {
Closure(Closure),
BoolLit(bool),
NaturalLit(Natural),
- EmptyOptionalLit(NormalizationContext, InputSubExpr),
- NEOptionalLit(NormalizationContext, InputSubExpr),
- EmptyListLit(NormalizationContext, InputSubExpr),
- NEListLit(Vec<(NormalizationContext, Vec<InputSubExpr>)>),
- RecordLit(NormalizationContext, BTreeMap<Label, InputSubExpr>),
+ EmptyOptionalLit(Now),
+ NEOptionalLit(Now),
+ EmptyListLit(Now),
+ NEListLit(Vec<Now>),
+ RecordLit(BTreeMap<Label, Now>),
UnionType(NormalizationContext, BTreeMap<Label, Option<InputSubExpr>>),
UnionLit(
Label,
- Box<WHNF>,
+ Now,
(NormalizationContext, BTreeMap<Label, Option<InputSubExpr>>),
),
Expr(OutputSubExpr),
@@ -236,29 +236,23 @@ impl WHNF {
WHNF::Closure(c) => c.normalize_to_expr(),
WHNF::BoolLit(b) => rc(ExprF::BoolLit(b)),
WHNF::NaturalLit(n) => rc(ExprF::NaturalLit(n)),
- WHNF::EmptyOptionalLit(ctx, e) => rc(ExprF::EmptyOptionalLit(
- normalize_whnf(&ctx, e).normalize_to_expr(),
- )),
- WHNF::NEOptionalLit(ctx, e) => rc(ExprF::NEOptionalLit(
- normalize_whnf(&ctx, e).normalize_to_expr(),
- )),
- WHNF::EmptyListLit(ctx, e) => rc(ExprF::EmptyListLit(
- normalize_whnf(&ctx, e).normalize_to_expr(),
- )),
+ WHNF::EmptyOptionalLit(n) => {
+ rc(ExprF::EmptyOptionalLit(n.normalize().normalize_to_expr()))
+ }
+ WHNF::NEOptionalLit(n) => {
+ rc(ExprF::NEOptionalLit(n.normalize().normalize_to_expr()))
+ }
+ WHNF::EmptyListLit(n) => {
+ rc(ExprF::EmptyListLit(n.normalize().normalize_to_expr()))
+ }
WHNF::NEListLit(elts) => rc(ExprF::NEListLit(
elts.into_iter()
- .flat_map(|(ctx, vs)| {
- vs.into_iter().map(move |v| {
- normalize_whnf(&ctx, v).normalize_to_expr()
- })
- })
+ .map(|n| n.normalize().normalize_to_expr())
.collect(),
)),
- WHNF::RecordLit(ctx, kvs) => rc(ExprF::RecordLit(
+ WHNF::RecordLit(kvs) => rc(ExprF::RecordLit(
kvs.into_iter()
- .map(|(k, v)| {
- (k, normalize_whnf(&ctx, v).normalize_to_expr())
- })
+ .map(|(k, v)| (k, v.normalize().normalize_to_expr()))
.collect(),
)),
WHNF::UnionType(ctx, kts) => rc(ExprF::UnionType(
@@ -275,7 +269,7 @@ impl WHNF {
)),
WHNF::UnionLit(l, v, (kts_ctx, kts)) => rc(ExprF::UnionLit(
l,
- v.normalize_to_expr(),
+ v.normalize().normalize_to_expr(),
kts.into_iter()
.map(|(k, v)| {
(
@@ -297,31 +291,19 @@ impl WHNF {
WHNF::Expr(e) => WHNF::Expr(shift0(delta, label, &e)),
WHNF::BoolLit(b) => WHNF::BoolLit(b),
WHNF::NaturalLit(n) => WHNF::NaturalLit(n),
- WHNF::EmptyOptionalLit(ctx, e) => {
- WHNF::EmptyOptionalLit(ctx, shift0(delta, label, &e))
+ WHNF::EmptyOptionalLit(n) => {
+ WHNF::EmptyOptionalLit(n.shift0(delta, label))
}
- WHNF::NEOptionalLit(ctx, e) => {
- WHNF::NEOptionalLit(ctx, shift0(delta, label, &e))
- }
- WHNF::EmptyListLit(ctx, e) => {
- WHNF::EmptyListLit(ctx, shift0(delta, label, &e))
+ WHNF::NEOptionalLit(n) => {
+ WHNF::NEOptionalLit(n.shift0(delta, label))
}
+ WHNF::EmptyListLit(n) => WHNF::EmptyListLit(n.shift0(delta, label)),
WHNF::NEListLit(elts) => WHNF::NEListLit(
- elts.into_iter()
- .map(|(ctx, vs)| {
- (
- ctx,
- vs.into_iter()
- .map(|v| shift0(delta, label, &v))
- .collect(),
- )
- })
- .collect(),
+ elts.into_iter().map(|n| n.shift0(delta, label)).collect(),
),
- WHNF::RecordLit(ctx, kvs) => WHNF::RecordLit(
- ctx,
+ WHNF::RecordLit(kvs) => WHNF::RecordLit(
kvs.into_iter()
- .map(|(k, v)| (k, shift0(delta, label, &v)))
+ .map(|(k, v)| (k, v.shift0(delta, label)))
.collect(),
),
WHNF::UnionType(ctx, kts) => WHNF::UnionType(
@@ -332,7 +314,7 @@ impl WHNF {
),
WHNF::UnionLit(l, v, (kts_ctx, kts)) => WHNF::UnionLit(
l,
- Box::new(v.shift0(delta, label)),
+ v.shift0(delta, label),
(
kts_ctx,
kts.into_iter()
@@ -344,9 +326,46 @@ impl WHNF {
}
}
+/// Normalize-on-write smart container. Contains either a (partially) normalized value or a
+/// non-normalized value alongside a normalization context.
+/// The name is a pun on std::borrow::Cow.
+#[derive(Debug, Clone)]
+enum Now {
+ Normalized(Box<WHNF>),
+ Unnormalized(NormalizationContext, InputSubExpr),
+}
+
+impl Now {
+ fn new(ctx: NormalizationContext, e: InputSubExpr) -> Now {
+ Now::Unnormalized(ctx, e)
+ }
+
+ fn from_whnf(v: WHNF) -> Now {
+ Now::Normalized(Box::new(v))
+ }
+
+ fn normalize(self) -> WHNF {
+ match self {
+ Now::Normalized(v) => *v,
+ Now::Unnormalized(ctx, e) => normalize_whnf(&ctx, e),
+ }
+ }
+
+ fn shift0(self, delta: isize, label: &Label) -> Self {
+ match self {
+ Now::Normalized(v) => {
+ Now::Normalized(Box::new(v.shift0(delta, label)))
+ }
+ Now::Unnormalized(ctx, e) => {
+ Now::Unnormalized(ctx, shift0(delta, label, &e))
+ }
+ }
+ }
+}
+
#[derive(Debug, Clone)]
enum Closure {
- Lam(NormalizationContext, Label, InputSubExpr, InputSubExpr),
+ Lam(Label, Now, (NormalizationContext, InputSubExpr)),
AppliedBuiltin(NormalizationContext, Builtin, Vec<WHNF>),
UnionConstructor(
NormalizationContext,
@@ -359,7 +378,7 @@ impl Closure {
/// Apply the closure to a value
fn app(self, val: WHNF) -> WHNF {
match self {
- Closure::Lam(ctx, x, _, e) => {
+ Closure::Lam(x, _, (ctx, e)) => {
let ctx2 = ctx.insert(&x, val);
normalize_whnf(&ctx2, e)
}
@@ -373,7 +392,7 @@ impl Closure {
}
}
Closure::UnionConstructor(ctx, l, kts) => {
- WHNF::UnionLit(l, Box::new(val), (ctx, kts))
+ WHNF::UnionLit(l, Now::from_whnf(val), (ctx, kts))
}
}
}
@@ -381,11 +400,11 @@ impl Closure {
/// Convert the closure back to a (normalized) syntactic expression
fn normalize_to_expr(self) -> OutputSubExpr {
match self {
- Closure::Lam(ctx, x, t, e) => {
+ Closure::Lam(x, t, (ctx, e)) => {
let ctx2 = ctx.skip(&x);
rc(ExprF::Lam(
x.clone(),
- normalize_whnf(&ctx, t).normalize_to_expr(),
+ t.normalize().normalize_to_expr(),
normalize_whnf(&ctx2, e).normalize_to_expr(),
))
}
@@ -419,11 +438,10 @@ impl Closure {
fn shift0(self, delta: isize, label: &Label) -> Self {
match self {
- Closure::Lam(ctx, x, t, e) => Closure::Lam(
- ctx,
+ Closure::Lam(x, t, (ctx, e)) => Closure::Lam(
x,
- shift0(delta, label, &t),
- shift(delta, &V(label.clone(), 1), &e),
+ t.shift0(delta, label),
+ (ctx, shift(delta, &V(label.clone(), 1), &e)),
),
Closure::AppliedBuiltin(ctx, b, args) => Closure::AppliedBuiltin(
ctx,
@@ -508,25 +526,35 @@ impl<'a> WhatNext<'a, X, X> {
fn reval(ctx: &NormalizationContext, expr: OutputSubExpr) -> WHNF {
match expr.as_ref().embed_absurd() {
- ExprF::Lam(x, t, e) => {
- WHNF::Closure(Closure::Lam(ctx.clone(), x, t, e))
- }
+ ExprF::Lam(x, t, e) => WHNF::Closure(Closure::Lam(
+ x,
+ Now::new(ctx.clone(), t),
+ (ctx.clone(), e),
+ )),
ExprF::Builtin(b) => {
WHNF::Closure(Closure::AppliedBuiltin(ctx.clone(), b, vec![]))
}
ExprF::BoolLit(b) => WHNF::BoolLit(b),
ExprF::NaturalLit(n) => WHNF::NaturalLit(n),
- ExprF::EmptyOptionalLit(e) => WHNF::EmptyOptionalLit(ctx.clone(), e),
- ExprF::NEOptionalLit(e) => WHNF::NEOptionalLit(ctx.clone(), e),
- ExprF::EmptyListLit(e) => WHNF::EmptyListLit(ctx.clone(), e),
- ExprF::NEListLit(elts) => WHNF::NEListLit(vec![(ctx.clone(), elts)]),
- ExprF::RecordLit(kvs) => WHNF::RecordLit(ctx.clone(), kvs),
- ExprF::UnionType(kvs) => WHNF::UnionType(ctx.clone(), kvs),
- ExprF::UnionLit(l, x, kts) => WHNF::UnionLit(
- l,
- Box::new(normalize_whnf(ctx, x)),
- (ctx.clone(), kts),
+ ExprF::EmptyOptionalLit(e) => {
+ WHNF::EmptyOptionalLit(Now::new(ctx.clone(), e))
+ }
+ ExprF::NEOptionalLit(e) => {
+ WHNF::NEOptionalLit(Now::new(ctx.clone(), e))
+ }
+ ExprF::EmptyListLit(e) => WHNF::EmptyListLit(Now::new(ctx.clone(), e)),
+ ExprF::NEListLit(elts) => WHNF::NEListLit(
+ elts.into_iter().map(|e| Now::new(ctx.clone(), e)).collect(),
+ ),
+ ExprF::RecordLit(kvs) => WHNF::RecordLit(
+ kvs.into_iter()
+ .map(|(k, e)| (k, Now::new(ctx.clone(), e)))
+ .collect(),
),
+ ExprF::UnionType(kvs) => WHNF::UnionType(ctx.clone(), kvs),
+ ExprF::UnionLit(l, x, kts) => {
+ WHNF::UnionLit(l, Now::new(ctx.clone(), x), (ctx.clone(), kts))
+ }
_ => WHNF::Expr(expr),
}
}
@@ -540,10 +568,9 @@ fn normalize_whnf(ctx: &NormalizationContext, expr: InputSubExpr) -> WHNF {
}
ExprF::Lam(x, t, e) => {
return WHNF::Closure(Closure::Lam(
- ctx.clone(),
x.clone(),
- t.clone(),
- e.clone(),
+ Now::new(ctx.clone(), t.clone()),
+ (ctx.clone(), e.clone()),
))
}
ExprF::Builtin(b) => {
@@ -555,26 +582,34 @@ fn normalize_whnf(ctx: &NormalizationContext, expr: InputSubExpr) -> WHNF {
}
ExprF::BoolLit(b) => return WHNF::BoolLit(*b),
ExprF::NaturalLit(n) => return WHNF::NaturalLit(*n),
- ExprF::OldOptionalLit(None, t) => {
- return WHNF::EmptyOptionalLit(ctx.clone(), t.clone())
+ ExprF::OldOptionalLit(None, e) => {
+ return WHNF::EmptyOptionalLit(Now::new(ctx.clone(), e.clone()))
}
- ExprF::OldOptionalLit(Some(x), _) => {
- return WHNF::NEOptionalLit(ctx.clone(), x.clone())
+ ExprF::OldOptionalLit(Some(e), _) => {
+ return WHNF::NEOptionalLit(Now::new(ctx.clone(), e.clone()))
}
ExprF::EmptyOptionalLit(e) => {
- return WHNF::EmptyOptionalLit(ctx.clone(), e.clone())
+ return WHNF::EmptyOptionalLit(Now::new(ctx.clone(), e.clone()))
}
ExprF::NEOptionalLit(e) => {
- return WHNF::NEOptionalLit(ctx.clone(), e.clone())
+ return WHNF::NEOptionalLit(Now::new(ctx.clone(), e.clone()))
}
ExprF::EmptyListLit(e) => {
- return WHNF::EmptyListLit(ctx.clone(), e.clone())
+ return WHNF::EmptyListLit(Now::new(ctx.clone(), e.clone()))
}
ExprF::NEListLit(elts) => {
- return WHNF::NEListLit(vec![(ctx.clone(), elts.clone())])
+ return WHNF::NEListLit(
+ elts.iter()
+ .map(|e| Now::new(ctx.clone(), e.clone()))
+ .collect(),
+ )
}
ExprF::RecordLit(kvs) => {
- return WHNF::RecordLit(ctx.clone(), kvs.clone())
+ return WHNF::RecordLit(
+ kvs.iter()
+ .map(|(k, e)| (k.clone(), Now::new(ctx.clone(), e.clone())))
+ .collect(),
+ )
}
ExprF::UnionType(kvs) => {
return WHNF::UnionType(ctx.clone(), kvs.clone())
@@ -582,7 +617,7 @@ fn normalize_whnf(ctx: &NormalizationContext, expr: InputSubExpr) -> WHNF {
ExprF::UnionLit(l, x, kts) => {
return WHNF::UnionLit(
l.clone(),
- Box::new(normalize_whnf(ctx, x.clone())),
+ Now::new(ctx.clone(), x.clone()),
(ctx.clone(), kts.clone()),
)
}
@@ -661,64 +696,60 @@ fn normalize_last_layer(
return WHNF::NaturalLit(x * y)
}
- BinOp(ListAppend, WHNF::EmptyListLit(_, _), y) => return y,
- BinOp(ListAppend, x, WHNF::EmptyListLit(_, _)) => return x,
- BinOp(ListAppend, WHNF::NEListLit(xs), WHNF::NEListLit(ys)) => {
- let xs = xs.into_iter();
- let ys = ys.into_iter();
- return WHNF::NEListLit(xs.chain(ys).collect());
+ BinOp(ListAppend, WHNF::EmptyListLit(_), y) => return y,
+ BinOp(ListAppend, x, WHNF::EmptyListLit(_)) => return x,
+ BinOp(ListAppend, WHNF::NEListLit(mut xs), WHNF::NEListLit(mut ys)) => {
+ xs.append(&mut ys);
+ return WHNF::NEListLit(xs);
}
Field(WHNF::UnionType(ctx, kts), l) => {
return WHNF::Closure(Closure::UnionConstructor(ctx, l, kts))
}
- Field(WHNF::RecordLit(record_ctx, mut kvs), l) => {
+ Field(WHNF::RecordLit(mut kvs), l) => {
match kvs.remove(&l) {
- Some(r) => return normalize_whnf(&record_ctx, r),
+ Some(r) => return r.normalize(),
// Return ownership
- None => Field(WHNF::RecordLit(record_ctx, kvs), l),
+ None => Field(WHNF::RecordLit(kvs), l),
}
}
// Always simplify `x.{}` to `{}`
Projection(_, ls) if ls.is_empty() => {
- return WHNF::RecordLit(
- ctx.clone(),
- std::collections::BTreeMap::new(),
- )
+ return WHNF::RecordLit(std::collections::BTreeMap::new())
}
- Projection(WHNF::RecordLit(record_ctx, mut kvs), ls) => {
+ Projection(WHNF::RecordLit(mut kvs), ls) => {
return WHNF::RecordLit(
- record_ctx,
ls.into_iter()
.filter_map(|l| kvs.remove(&l).map(|x| (l, x)))
.collect(),
)
}
Merge(
- WHNF::RecordLit(record_ctx, mut handlers),
+ WHNF::RecordLit(mut handlers),
WHNF::Closure(Closure::UnionConstructor(ctor_ctx, l, kts)),
t,
) => match handlers.remove(&l) {
- Some(h) => return normalize_whnf(ctx, h),
+ Some(h) => return h.normalize(),
// Return ownership
None => Merge(
- WHNF::RecordLit(record_ctx, handlers),
+ WHNF::RecordLit(handlers),
WHNF::Closure(Closure::UnionConstructor(ctor_ctx, l, kts)),
t,
),
},
Merge(
- WHNF::RecordLit(record_ctx, mut handlers),
+ WHNF::RecordLit(mut handlers),
WHNF::UnionLit(l, v, (kts_ctx, kts)),
t,
) => match handlers.remove(&l) {
Some(h) => {
- let h = normalize_whnf(&kts_ctx, h);
- return normalize_last_layer(ctx, App(h, *v));
+ let h = h.normalize();
+ let v = v.normalize();
+ return normalize_last_layer(ctx, App(h, v));
}
// Return ownership
None => Merge(
- WHNF::RecordLit(record_ctx, handlers),
+ WHNF::RecordLit(handlers),
WHNF::UnionLit(l, v, (kts_ctx, kts)),
t,
),