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-rw-r--r--dhall_core/src/core.rs290
1 files changed, 4 insertions, 286 deletions
diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs
index 340cb04..0787862 100644
--- a/dhall_core/src/core.rs
+++ b/dhall_core/src/core.rs
@@ -233,21 +233,21 @@ impl<'i, S, A> From<Builtin> for Expr<'i, S, A> {
}
impl<'i, S, A> Expr<'i, S, A> {
- fn bool_lit(&self) -> Option<bool> {
+ pub fn bool_lit(&self) -> Option<bool> {
match *self {
Expr::BoolLit(v) => Some(v),
_ => None,
}
}
- fn natural_lit(&self) -> Option<usize> {
+ pub fn natural_lit(&self) -> Option<usize> {
match *self {
Expr::NaturalLit(v) => Some(v),
_ => None,
}
}
- fn text_lit(&self) -> Option<String> {
+ pub fn text_lit(&self) -> Option<String> {
match *self {
Expr::TextLit(ref t) => Some(t.clone()), // FIXME?
_ => None,
@@ -630,7 +630,7 @@ fn add_ui(u: usize, i: isize) -> usize {
}
}
-fn map_record_value<'a, I, K, V, U, F>(it: I, f: F) -> BTreeMap<K, U>
+pub fn map_record_value<'a, I, K, V, U, F>(it: I, f: F) -> BTreeMap<K, U>
where
I: IntoIterator<Item = (&'a K, &'a V)>,
K: Eq + Ord + Copy + 'a,
@@ -921,285 +921,3 @@ where
map_op2(f, |x| bx(subst(v, e, x)), a, b)
}
-/// Reduce an expression to its normal form, performing beta reduction
-///
-/// `normalize` does not type-check the expression. You may want to type-check
-/// expressions before normalizing them since normalization can convert an
-/// ill-typed expression into a well-typed expression.
-///
-/// However, `normalize` will not fail if the expression is ill-typed and will
-/// leave ill-typed sub-expressions unevaluated.
-///
-pub fn normalize<'i, S, T, A>(e: &Expr<'i, S, A>) -> Expr<'i, T, A>
-where
- S: Clone + fmt::Debug,
- T: Clone + fmt::Debug,
- A: Clone + fmt::Debug,
-{
- use crate::BinOp::*;
- use crate::Builtin::*;
- use crate::Expr::*;
- match *e {
- Const(k) => Const(k),
- Var(v) => Var(v),
- Lam(x, ref tA, ref b) => {
- let tA2 = normalize(tA);
- let b2 = normalize(b);
- Lam(x, bx(tA2), bx(b2))
- }
- Pi(x, ref tA, ref tB) => {
- let tA2 = normalize(tA);
- let tB2 = normalize(tB);
- pi(x, tA2, tB2)
- }
- App(ref f, ref a) => match normalize::<S, T, A>(f) {
- Lam(x, _A, b) => {
- // Beta reduce
- let vx0 = V(x, 0);
- let a2 = shift::<S, S, A>(1, vx0, a);
- let b2 = subst::<S, T, A>(vx0, &a2, &b);
- let b3 = shift::<S, T, A>(-1, vx0, &b2);
- normalize(&b3)
- }
- f2 => match (f2, normalize::<S, T, A>(a)) {
- // fold/build fusion for `List`
- (App(box Builtin(ListBuild), _), App(box App(box Builtin(ListFold), _), box e2)) |
- (App(box Builtin(ListFold), _), App(box App(box Builtin(ListBuild), _), box e2)) |
-
- // fold/build fusion for `Natural`
- (Builtin(NaturalBuild), App(box Builtin(NaturalFold), box e2)) |
- (Builtin(NaturalFold), App(box Builtin(NaturalBuild), box e2)) => normalize(&e2),
-
- /*
- App (App (App (App NaturalFold (NaturalLit n0)) _) succ') zero ->
- normalize (go n0)
- where
- go !0 = zero
- go !n = App succ' (go (n - 1))
- App NaturalBuild k
- | check -> NaturalLit n
- | otherwise -> App f' a'
- where
- labeled =
- normalize (App (App (App k Natural) "Succ") "Zero")
-
- n = go 0 labeled
- where
- go !m (App (Var "Succ") e') = go (m + 1) e'
- go !m (Var "Zero") = m
- go !_ _ = internalError text
- check = go labeled
- where
- go (App (Var "Succ") e') = go e'
- go (Var "Zero") = True
- go _ = False
- */
- (Builtin(NaturalIsZero), NaturalLit(n)) => BoolLit(n == 0),
- (Builtin(NaturalEven), NaturalLit(n)) => BoolLit(n % 2 == 0),
- (Builtin(NaturalOdd), NaturalLit(n)) => BoolLit(n % 2 != 0),
- (Builtin(NaturalToInteger), NaturalLit(n)) => IntegerLit(n as isize),
- (Builtin(NaturalShow), NaturalLit(n)) => TextLit(n.to_string()),
- (App(f@box Builtin(ListBuild), box t), k) => {
- let labeled =
- normalize::<_, T, _>(&app(app(app(k.clone(), app(
- Builtin(self::Builtin::List), t.clone())), "Cons"), "Nil"));
-
- fn list_to_vector<'i, S, A>(v: &mut Vec<Expr<'i, S, A>>, e: Expr<'i, S, A>)
- where S: Clone, A: Clone
- {
- match e {
- App(box App(box Var(V("Cons", _)), box x), box e2) => {
- v.push(x);
- list_to_vector(v, e2)
- }
- Var(V("Nil", _)) => {}
- _ => panic!("internalError list_to_vector"),
- }
- }
- fn check<S, A>(e: &Expr<S, A>) -> bool {
- match *e {
- App(box App(box Var(V("Cons", _)), _), ref e2) => check(e2),
- Var(V("Nil", _)) => true,
- _ => false,
- }
- }
-
- if check(&labeled) {
- let mut v = vec![];
- list_to_vector(&mut v, labeled);
- ListLit(Some(bx(t)), v)
- } else {
- app(App(f, bx(t)), k)
- }
- }
- (App(box App(box App(box App(box Builtin(ListFold), _), box ListLit(_, xs)), _), cons), nil) => {
- let e2: Expr<_, _> = xs.into_iter().rev().fold(nil, |y, ys| // foldr
- App(bx(App(cons.clone(), bx(y))), bx(ys))
- );
- normalize(&e2)
- }
- (App(f, x_), ListLit(t, ys)) => match *f {
- Builtin(ListLength) =>
- NaturalLit(ys.len()),
- Builtin(ListHead) =>
- normalize(&OptionalLit(t, ys.into_iter().take(1).collect())),
- Builtin(ListLast) =>
- normalize(&OptionalLit(t, ys.into_iter().last().into_iter().collect())),
- Builtin(ListReverse) => {
- let mut xs = ys;
- xs.reverse();
- normalize(&ListLit(t, xs))
- }
- _ => app(App(f, x_), ListLit(t, ys)),
- },
- /*
- App (App ListIndexed _) (ListLit t xs) ->
- normalize (ListLit t' (fmap adapt (Data.Vector.indexed xs)))
- where
- t' = Record (Data.Map.fromList kts)
- where
- kts = [ ("index", Natural)
- , ("value", t)
- ]
- adapt (n, x) = RecordLit (Data.Map.fromList kvs)
- where
- kvs = [ ("index", NaturalLit (fromIntegral n))
- , ("value", x)
- ]
- */
- (App(box App(box App(box App(box Builtin(OptionalFold), _), box OptionalLit(_, xs)), _), just), nothing) => {
- let e2: Expr<_, _> = xs.into_iter().fold(nothing, |y, _|
- App(just.clone(), bx(y))
- );
- normalize(&e2)
- }
- (App(box Builtin(OptionalBuild), _), App(box App(box Builtin(OptionalFold), _), b)) => {
- normalize(&b)
- }
- (App(box Builtin(OptionalBuild), a0), g) => {
- let e2: Expr<_, _> = app(app(app(g,
- App(bx(Builtin(Optional)), a0.clone())),
- Lam("x", a0.clone(),
- bx(OptionalLit(Some(a0.clone()), vec![Var(V("x", 0))])))),
- OptionalLit(Some(a0), vec![]));
- normalize(&e2)
- }
- (f2, a2) => app(f2, a2),
- },
- },
- Let(f, _, ref r, ref b) => {
- let r2 = shift::<_, S, _>(1, V(f, 0), r);
- let b2 = subst(V(f, 0), &r2, b);
- let b3 = shift::<_, T, _>(-1, V(f, 0), &b2);
- normalize(&b3)
- }
- Annot(ref x, _) => normalize(x),
- Builtin(v) => Builtin(v),
- BoolLit(b) => BoolLit(b),
- BinOp(BoolAnd, ref x, ref y) => with_binop(
- BoolAnd,
- Expr::bool_lit,
- |xn, yn| BoolLit(xn && yn),
- normalize(x),
- normalize(y),
- ),
- BinOp(BoolOr, ref x, ref y) => with_binop(
- BoolOr,
- Expr::bool_lit,
- |xn, yn| BoolLit(xn || yn),
- normalize(x),
- normalize(y),
- ),
- BinOp(BoolEQ, ref x, ref y) => with_binop(
- BoolEQ,
- Expr::bool_lit,
- |xn, yn| BoolLit(xn == yn),
- normalize(x),
- normalize(y),
- ),
- BinOp(BoolNE, ref x, ref y) => with_binop(
- BoolNE,
- Expr::bool_lit,
- |xn, yn| BoolLit(xn != yn),
- normalize(x),
- normalize(y),
- ),
- BoolIf(ref b, ref t, ref f) => match normalize(b) {
- BoolLit(true) => normalize(t),
- BoolLit(false) => normalize(f),
- b2 => BoolIf(bx(b2), bx(normalize(t)), bx(normalize(f))),
- },
- NaturalLit(n) => NaturalLit(n),
- BinOp(NaturalPlus, ref x, ref y) => with_binop(
- NaturalPlus,
- Expr::natural_lit,
- |xn, yn| NaturalLit(xn + yn),
- normalize(x),
- normalize(y),
- ),
- BinOp(NaturalTimes, ref x, ref y) => with_binop(
- NaturalTimes,
- Expr::natural_lit,
- |xn, yn| NaturalLit(xn * yn),
- normalize(x),
- normalize(y),
- ),
- IntegerLit(n) => IntegerLit(n),
- DoubleLit(n) => DoubleLit(n),
- TextLit(ref t) => TextLit(t.clone()),
- BinOp(TextAppend, ref x, ref y) => with_binop(
- TextAppend,
- Expr::text_lit,
- |xt, yt| TextLit(xt + &yt),
- normalize(x),
- normalize(y),
- ),
- ListLit(ref t, ref es) => {
- let t2 = t.as_ref().map(|x| x.as_ref()).map(normalize).map(bx);
- let es2 = es.iter().map(normalize).collect();
- ListLit(t2, es2)
- }
- OptionalLit(ref t, ref es) => {
- let t2 = t.as_ref().map(|x| x.as_ref()).map(normalize).map(bx);
- let es2 = es.iter().map(normalize).collect();
- OptionalLit(t2, es2)
- }
- Record(ref kts) => Record(map_record_value(kts, normalize)),
- RecordLit(ref kvs) => RecordLit(map_record_value(kvs, normalize)),
- Union(ref kts) => Union(map_record_value(kts, normalize)),
- UnionLit(k, ref v, ref kvs) => {
- UnionLit(k, bx(normalize(v)), map_record_value(kvs, normalize))
- }
- Merge(ref _x, ref _y, ref _t) => unimplemented!(),
- Field(ref r, x) => match normalize(r) {
- RecordLit(kvs) => match kvs.get(x) {
- Some(r2) => normalize(r2),
- None => {
- Field(bx(RecordLit(map_record_value(&kvs, normalize))), x)
- }
- },
- r2 => Field(bx(r2), x),
- },
- Note(_, ref e) => normalize(e),
- Embed(ref a) => Embed(a.clone()),
- _ => unimplemented!(),
- }
-}
-
-fn with_binop<'a, S, A, U, Get, Set>(
- op: BinOp,
- get: Get,
- set: Set,
- x: Expr<'a, S, A>,
- y: Expr<'a, S, A>,
-) -> Expr<'a, S, A>
-where
- Get: Fn(&Expr<'a, S, A>) -> Option<U>,
- Set: FnOnce(U, U) -> Expr<'a, S, A>,
-{
- if let (Some(xv), Some(yv)) = (get(&x), get(&y)) {
- set(xv, yv)
- } else {
- Expr::BinOp(op, bx(x), bx(y))
- }
-}
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