diff options
Diffstat (limited to '')
| -rw-r--r-- | dhall/src/normalize.rs | 433 | ||||
| -rw-r--r-- | dhall/src/typecheck.rs | 6 |
2 files changed, 206 insertions, 233 deletions
diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs index 966d032..cd4669d 100644 --- a/dhall/src/normalize.rs +++ b/dhall/src/normalize.rs @@ -3,82 +3,60 @@ use dhall_core::*; use dhall_generator::dhall_expr; use std::fmt; -fn apply_builtin<S, A>( - b: Builtin, - mut args: Vec<SubExpr<S, A>>, -) -> SubExpr<S, A> +fn apply_builtin<S, A>(b: Builtin, args: &Vec<Expr<S, A>>) -> WhatNext<S, A> where - S: fmt::Debug, - A: fmt::Debug, + S: fmt::Debug + Clone, + A: fmt::Debug + Clone, { use dhall_core::Builtin::*; use dhall_core::ExprF::*; - let f = rc(Builtin(b)); - // How many arguments a builtin needs, and which argument - // should be normalized and pattern-matched - let (len_consumption, arg_to_eval) = match b { - OptionalSome => (1, None), - OptionalNone => (1, None), - NaturalIsZero => (1, Some(0)), - NaturalEven => (1, Some(0)), - NaturalOdd => (1, Some(0)), - NaturalToInteger => (1, Some(0)), - NaturalShow => (1, Some(0)), - ListLength => (2, Some(1)), - ListHead => (2, Some(1)), - ListLast => (2, Some(1)), - ListReverse => (2, Some(1)), - ListIndexed => (2, Some(1)), - ListBuild => (2, Some(1)), - OptionalBuild => (2, Some(1)), - ListFold => (5, Some(1)), - OptionalFold => (5, Some(1)), - NaturalBuild => (1, Some(0)), - NaturalFold => (4, Some(0)), - _ => (0, None), - }; - // Abort if not enough arguments present - if len_consumption > args.len() { - return rc(App(f, args)); - } - // Normalize the important argument - if let Some(i) = arg_to_eval { - args[i] = SubExpr::clone(&normalize_whnf(&args[i])); - } - let evaled_arg = arg_to_eval.map(|i| args[i].as_ref()); - - let ret = match (b, evaled_arg, args.as_slice()) { - (OptionalSome, _, [x, ..]) => rc(NEOptionalLit(SubExpr::clone(x))), - (OptionalNone, _, [t, ..]) => rc(EmptyOptionalLit(SubExpr::clone(t))), - (NaturalIsZero, Some(NaturalLit(n)), _) => rc(BoolLit(*n == 0)), - (NaturalEven, Some(NaturalLit(n)), _) => rc(BoolLit(*n % 2 == 0)), - (NaturalOdd, Some(NaturalLit(n)), _) => rc(BoolLit(*n % 2 != 0)), - (NaturalToInteger, Some(NaturalLit(n)), _) => { - rc(IntegerLit(*n as isize)) + use WhatNext::*; + let (ret, rest) = match (b, args.as_slice()) { + (OptionalSome, [x, rest..]) => (rc(NEOptionalLit(x.roll())), rest), + (OptionalNone, [t, rest..]) => (rc(EmptyOptionalLit(t.roll())), rest), + (NaturalIsZero, [NaturalLit(n), rest..]) => { + (rc(BoolLit(*n == 0)), rest) } - (NaturalShow, Some(NaturalLit(n)), _) => { - rc(TextLit(n.to_string().into())) + (NaturalEven, [NaturalLit(n), rest..]) => { + (rc(BoolLit(*n % 2 == 0)), rest) } - (ListLength, Some(EmptyListLit(_)), _) => rc(NaturalLit(0)), - (ListLength, Some(NEListLit(ys)), _) => rc(NaturalLit(ys.len())), - (ListHead, Some(EmptyListLit(t)), _) => rc(EmptyOptionalLit(t.clone())), - (ListHead, Some(NEListLit(ys)), _) => { - rc(NEOptionalLit(ys.first().unwrap().clone())) + (NaturalOdd, [NaturalLit(n), rest..]) => { + (rc(BoolLit(*n % 2 != 0)), rest) } - (ListLast, Some(EmptyListLit(t)), _) => rc(EmptyOptionalLit(t.clone())), - (ListLast, Some(NEListLit(ys)), _) => { - rc(NEOptionalLit(ys.last().unwrap().clone())) + (NaturalToInteger, [NaturalLit(n), rest..]) => { + (rc(IntegerLit(*n as isize)), rest) } - (ListReverse, Some(EmptyListLit(t)), _) => rc(EmptyListLit(t.clone())), - (ListReverse, Some(NEListLit(ys)), _) => { - let ys = ys.iter().rev().cloned().collect(); - rc(NEListLit(ys)) + (NaturalShow, [NaturalLit(n), rest..]) => { + (rc(TextLit(n.to_string().into())), rest) + } + (ListLength, [_, EmptyListLit(_), rest..]) => (rc(NaturalLit(0)), rest), + (ListLength, [_, NEListLit(ys), rest..]) => { + (rc(NaturalLit(ys.len())), rest) + } + (ListHead, [_, EmptyListLit(t), rest..]) => { + (rc(EmptyOptionalLit(t.clone())), rest) + } + (ListHead, [_, NEListLit(ys), rest..]) => { + (rc(NEOptionalLit(ys.first().unwrap().clone())), rest) } - (ListIndexed, Some(EmptyListLit(t)), _) => { - let t = SubExpr::clone(t); - dhall_expr!([] : List ({ index : Natural, value : t })) + (ListLast, [_, EmptyListLit(t), rest..]) => { + (rc(EmptyOptionalLit(t.clone())), rest) } - (ListIndexed, Some(NEListLit(xs)), _) => { + (ListLast, [_, NEListLit(ys), rest..]) => { + (rc(NEOptionalLit(ys.last().unwrap().clone())), rest) + } + (ListReverse, [_, EmptyListLit(t), rest..]) => { + (rc(EmptyListLit(t.clone())), rest) + } + (ListReverse, [_, NEListLit(ys), rest..]) => { + let ys = ys.iter().rev().cloned().collect(); + (rc(NEListLit(ys)), rest) + } + (ListIndexed, [_, EmptyListLit(t), rest..]) => ( + dhall_expr!([] : List ({ index : Natural, value : t })), + rest, + ), + (ListIndexed, [_, NEListLit(xs), rest..]) => { let xs = xs .iter() .cloned() @@ -88,102 +66,110 @@ where dhall_expr!({ index = i, value = e }) }) .collect(); - rc(NEListLit(xs)) + (rc(NEListLit(xs)), rest) } - (ListBuild, _, [a0, g, ..]) => { + (ListBuild, [a0, g, rest..]) => { loop { - if let App(f2, args2) = g.as_ref() { - if let (Builtin(ListFold), [_, x, rest..]) = + if let App(f2, args2) = g { + if let (Builtin(ListFold), [_, x, rest_inner..]) = (f2.as_ref(), args2.as_slice()) { // fold/build fusion - break rc(App(x.clone(), rest.to_vec())); + break (rc(App(x.clone(), rest_inner.to_vec())), rest); } }; - let a0 = SubExpr::clone(a0); + let a0 = a0.roll(); let a1 = shift(1, &V("a".into(), 0), &a0); - // TODO: use Embed to avoid reevaluating g - break dhall_expr!( - g - (List a0) - (λ(a : a0) -> λ(as : List a1) -> [ a ] # as) - ([] : List a0) + let g = g.roll(); + break ( + dhall_expr!( + g + (List a0) + (λ(a : a0) -> λ(as : List a1) -> [ a ] # as) + ([] : List a0) + ), + rest, ); } } - (OptionalBuild, _, [a0, g, ..]) => { + (OptionalBuild, [a0, g, rest..]) => { loop { - if let App(f2, args2) = g.as_ref() { - if let (Builtin(OptionalFold), [_, x, rest..]) = + if let App(f2, args2) = g { + if let (Builtin(OptionalFold), [_, x, rest_inner..]) = (f2.as_ref(), args2.as_slice()) { // fold/build fusion - break rc(App(x.clone(), rest.to_vec())); + break (rc(App(x.clone(), rest_inner.to_vec())), rest); } }; - let a0 = SubExpr::clone(a0); - // TODO: use Embed to avoid reevaluating g - break dhall_expr!( - g - (Optional a0) - (λ(x: a0) -> Some x) - (None a0) + let a0 = a0.roll(); + let g = g.roll(); + break ( + dhall_expr!( + g + (Optional a0) + (λ(x: a0) -> Some x) + (None a0) + ), + rest, ); } } - (ListFold, Some(EmptyListLit(_)), [_, _, _, _, nil, ..]) => { - SubExpr::clone(nil) + (ListFold, [_, EmptyListLit(_), _, _, nil, rest..]) => { + (nil.roll(), rest) } - (ListFold, Some(NEListLit(xs)), [_, _, _, cons, nil, ..]) => { - xs.iter().rev().fold(SubExpr::clone(nil), |acc, x| { + (ListFold, [_, NEListLit(xs), _, cons, nil, rest..]) => ( + xs.iter().rev().fold(nil.roll(), |acc, x| { let x = x.clone(); let acc = acc.clone(); - let cons = SubExpr::clone(cons); + let cons = cons.roll(); dhall_expr!(cons x acc) - }) - } + }), + rest, + ), // // fold/build fusion // (ListFold, [_, App(box Builtin(ListBuild), [_, x, rest..]), rest..]) => { - // normalize_whnf(&App(bx(x.clone()), rest.to_vec())) + // normalize_ref(&App(bx(x.clone()), rest.to_vec())) // } - (OptionalFold, Some(NEOptionalLit(x)), [_, _, _, just, _, ..]) => { + (OptionalFold, [_, NEOptionalLit(x), _, just, _, rest..]) => { let x = x.clone(); - let just = SubExpr::clone(just); - dhall_expr!(just x) + let just = just.roll(); + (dhall_expr!(just x), rest) + } + (OptionalFold, [_, EmptyOptionalLit(_), _, _, nothing, rest..]) => { + (nothing.roll(), rest) } - ( - OptionalFold, - Some(EmptyOptionalLit(_)), - [_, _, _, _, nothing, ..], - ) => SubExpr::clone(nothing), // // fold/build fusion // (OptionalFold, [_, App(box Builtin(OptionalBuild), [_, x, rest..]), rest..]) => { - // normalize_whnf(&App(bx(x.clone()), rest.to_vec())) + // normalize_ref(&App(bx(x.clone()), rest.to_vec())) // } - (NaturalBuild, _, [g, ..]) => { + (NaturalBuild, [g, rest..]) => { loop { - if let App(f2, args2) = g.as_ref() { - if let (Builtin(NaturalFold), [x, rest..]) = + if let App(f2, args2) = g { + if let (Builtin(NaturalFold), [x, rest_inner..]) = (f2.as_ref(), args2.as_slice()) { // fold/build fusion - break rc(App(x.clone(), rest.to_vec())); + break (rc(App(x.clone(), rest_inner.to_vec())), rest); } }; - // TODO: use Embed to avoid reevaluating g - break dhall_expr!(g Natural (λ(x : Natural) -> x + 1) 0); + let g = g.roll(); + break ( + dhall_expr!(g Natural (λ(x : Natural) -> x + 1) 0), + rest, + ); } } - (NaturalFold, Some(NaturalLit(0)), [_, _, _, zero]) => { - SubExpr::clone(zero) + (NaturalFold, [NaturalLit(0), _, _, zero, rest..]) => { + (zero.roll(), rest) } - (NaturalFold, Some(NaturalLit(n)), [_, t, succ, zero]) => { + (NaturalFold, [NaturalLit(n), t, succ, zero, rest..]) => { let fold = rc(Builtin(NaturalFold)); let n = rc(NaturalLit(n - 1)); - let t = SubExpr::clone(t); - let succ = SubExpr::clone(succ); - let zero = SubExpr::clone(zero); - dhall_expr!(succ (fold n t succ zero)) + let t = t.roll(); + let succ = succ.roll(); + let zero = zero.roll(); + (dhall_expr!(succ (fold n t succ zero)), rest) } // (NaturalFold, Some(App(f2, args2)), _) => { // match (f2.as_ref(), args2.as_slice()) { @@ -194,140 +180,127 @@ where // _ => return rc(App(f, args)), // } // } - _ => return rc(App(f, args)), + _ => return DoneAsIs, }; // Put the remaining arguments back and eval again. In most cases // ret will not be of a form that can be applied, so this won't go very deep. // In lots of cases, there are no remaining args so this cann will just return ret. - normalize_whnf(&rc(ExprF::App(ret, args.split_off(len_consumption)))) + let rest: Vec<SubExpr<S, A>> = rest.iter().map(ExprF::roll).collect(); + Continue(ExprF::App(ret, rest)) } -/// Reduce an expression to its weak head normal form, i.e. normalize -/// just enough to get the first constructor of the final expression -/// Is identical to normalize on primitive types, but not on more complex -/// types like functions and records. -/// This allows normalization to be lazy. -pub fn normalize_whnf<S, A>(e: &SubExpr<S, A>) -> SubExpr<S, A> +// Small enum to help with being DRY +enum WhatNext<'a, S, A> { + // Recurse on this expression + Continue(Expr<S, A>), + ContinueSub(SubExpr<S, A>), + // The following expression is the normal form + Done(Expr<S, A>), + DoneRef(&'a Expr<S, A>), + DoneRefSub(&'a SubExpr<S, A>), + // The current expression is already in normal form + DoneAsIs, +} + +pub fn normalize_ref<S, A>(expr: &Expr<S, A>) -> Expr<S, A> where - S: fmt::Debug, - A: fmt::Debug, + S: fmt::Debug + Clone, + A: fmt::Debug + Clone, { use dhall_core::BinOp::*; use dhall_core::ExprF::*; - match e.as_ref() { + // Recursively normalize all subexpressions + let expr: ExprF<Expr<S, A>, Label, S, A> = + expr.map_ref_simple(|e| normalize_ref(e.as_ref())); + + use WhatNext::*; + let what_next = match &expr { Let(f, _, r, b) => { let vf0 = &V(f.clone(), 0); - let r2 = shift(1, vf0, r); + let r2 = shift(1, vf0, &r.roll()); // TODO: use a context - let b2 = subst(vf0, &r2, b); + let b2 = subst(vf0, &r2, &b.roll()); // TODO: add tests sensitive to shift errors before // trying anything let b3 = shift(-1, vf0, &b2); - normalize_whnf(&b3) - } - Annot(x, _) => normalize_whnf(x), - Note(_, e) => normalize_whnf(e), - App(f, args) => { - let f = normalize_whnf(f); - match (f.as_ref(), args.as_slice()) { - (_, []) => f, - // TODO: use Embed to avoid reevaluating f - (App(f, args1), args2) => normalize_whnf(&rc(App( - f.clone(), - args1.iter().chain(args2.iter()).cloned().collect(), - ))), - (Lam(ref x, _, ref b), [a, rest..]) => { - // Beta reduce - let vx0 = &V(x.clone(), 0); - let a2 = shift(1, vx0, a); - let b2 = subst(vx0, &a2, &b); - let b3 = shift(-1, vx0, &b2); - normalize_whnf(&rc(App(b3, rest.to_vec()))) - } - (Builtin(b), _) => apply_builtin(*b, args.to_vec()), - _ => rc(App(f, args.to_vec())), - } + ContinueSub(b3) } - BoolIf(b, t, f) => { - let b = normalize_whnf(b); - match b.as_ref() { - BoolLit(true) => normalize_whnf(t), - BoolLit(false) => normalize_whnf(f), - _ => rc(BoolIf(b, t.clone(), f.clone())), - } + Annot(x, _) => DoneRef(x), + Note(_, e) => DoneRef(e), + App(f, args) if args.is_empty() => DoneRef(f), + App(App(f, args1), args2) => Continue(App( + f.clone(), + args1 + .iter() + .cloned() + .chain(args2.iter().map(ExprF::roll)) + .collect(), + )), + App(Builtin(b), args) => apply_builtin(*b, args), + App(Lam(x, _, b), args) => { + let mut iter = args.iter(); + // We know args is nonempty + let a = iter.next().unwrap(); + // Beta reduce + let vx0 = &V(x.clone(), 0); + let a2 = shift(1, vx0, &a.roll()); + let b2 = subst(vx0, &a2, &b); + let b3 = shift(-1, vx0, &b2); + Continue(App(b3, iter.map(ExprF::roll).collect())) } + BoolIf(BoolLit(true), t, _) => DoneRef(t), + BoolIf(BoolLit(false), _, f) => DoneRef(f), // TODO: interpolation // TextLit(t) => - BinOp(o, x, y) => { - let x = normalize_whnf(x); - let y = normalize_whnf(y); - rc(match (o, x.as_ref(), y.as_ref()) { - (BoolAnd, BoolLit(x), BoolLit(y)) => BoolLit(*x && *y), - (BoolOr, BoolLit(x), BoolLit(y)) => BoolLit(*x || *y), - (BoolEQ, BoolLit(x), BoolLit(y)) => BoolLit(x == y), - (BoolNE, BoolLit(x), BoolLit(y)) => BoolLit(x != y), - (NaturalPlus, NaturalLit(x), NaturalLit(y)) => { - NaturalLit(x + y) - } - (NaturalTimes, NaturalLit(x), NaturalLit(y)) => { - NaturalLit(x * y) - } - (TextAppend, TextLit(x), TextLit(y)) => TextLit(x + y), - (ListAppend, EmptyListLit(t), EmptyListLit(_)) => { - EmptyListLit(SubExpr::clone(t)) - } - (ListAppend, EmptyListLit(_), _) => return y, - (ListAppend, _, EmptyListLit(_)) => return x, - (ListAppend, NEListLit(xs), NEListLit(ys)) => { - let xs = xs.into_iter().cloned(); - let ys = ys.into_iter().cloned(); - NEListLit(xs.chain(ys).collect()) - } - (o, _, _) => BinOp(*o, x, y), - }) + BinOp(BoolAnd, BoolLit(x), BoolLit(y)) => Done(BoolLit(*x && *y)), + BinOp(BoolOr, BoolLit(x), BoolLit(y)) => Done(BoolLit(*x || *y)), + BinOp(BoolEQ, BoolLit(x), BoolLit(y)) => Done(BoolLit(x == y)), + BinOp(BoolNE, BoolLit(x), BoolLit(y)) => Done(BoolLit(x != y)), + BinOp(NaturalPlus, NaturalLit(x), NaturalLit(y)) => { + Done(NaturalLit(x + y)) } - Merge(x, y, t) => { - let x = normalize_whnf(x); - let y = normalize_whnf(y); - match (x.as_ref(), y.as_ref()) { - (RecordLit(handlers), UnionLit(k, v, _)) => { - match handlers.get(&k) { - Some(h) => { - normalize_whnf(&rc(App(h.clone(), vec![v.clone()]))) - } - None => rc(Merge(x, y, t.clone())), - } - } - _ => rc(Merge(x, y, t.clone())), - } + BinOp(NaturalTimes, NaturalLit(x), NaturalLit(y)) => { + Done(NaturalLit(x * y)) } - Field(e, l) => { - let e = normalize_whnf(e); - match e.as_ref() { - RecordLit(kvs) => match kvs.get(&l) { - Some(r) => normalize_whnf(r), - None => rc(Field(e, l.clone())), - }, - _ => rc(Field(e, l.clone())), - } + BinOp(TextAppend, TextLit(x), TextLit(y)) => Done(TextLit(x + y)), + BinOp(ListAppend, EmptyListLit(t), EmptyListLit(_)) => { + Done(EmptyListLit(SubExpr::clone(t))) } - Projection(_, ls) if ls.is_empty() => { - rc(RecordLit(std::collections::BTreeMap::new())) + BinOp(ListAppend, EmptyListLit(_), y) => DoneRef(y), + BinOp(ListAppend, x, EmptyListLit(_)) => DoneRef(x), + BinOp(ListAppend, NEListLit(xs), NEListLit(ys)) => { + let xs = xs.into_iter().cloned(); + let ys = ys.into_iter().cloned(); + Done(NEListLit(xs.chain(ys).collect())) } - Projection(e, ls) => { - let e = normalize_whnf(e); - match e.as_ref() { - RecordLit(kvs) => rc(RecordLit( - ls.iter() - .filter_map(|l| { - kvs.get(l).map(|x| (l.clone(), x.clone())) - }) - .collect(), - )), - _ => rc(Projection(e, ls.clone())), + Merge(RecordLit(handlers), UnionLit(k, v, _), _) => { + match handlers.get(&k) { + Some(h) => Continue(App(h.clone(), vec![v.clone()])), + None => DoneAsIs, } } - _ => SubExpr::clone(e), + Field(RecordLit(kvs), l) => match kvs.get(&l) { + Some(r) => DoneRefSub(r), + None => DoneAsIs, + }, + Projection(_, ls) if ls.is_empty() => { + Done(RecordLit(std::collections::BTreeMap::new())) + } + Projection(RecordLit(kvs), ls) => Done(RecordLit( + ls.iter() + .filter_map(|l| kvs.get(l).map(|x| (l.clone(), x.clone()))) + .collect(), + )), + _ => DoneAsIs, + }; + + match what_next { + Continue(e) => normalize_ref(&e), + ContinueSub(e) => normalize_ref(e.as_ref()), + Done(e) => e, + DoneRef(e) => e.clone(), + DoneRefSub(e) => e.unroll(), + DoneAsIs => expr.map_ref_simple(ExprF::roll), } } @@ -342,8 +315,8 @@ where /// pub fn normalize<S, A>(e: SubExpr<S, A>) -> SubExpr<S, A> where - S: fmt::Debug, - A: fmt::Debug, + S: fmt::Debug + Clone, + A: fmt::Debug + Clone, { - normalize_whnf(&e).map_ref_simple(|x| normalize(SubExpr::clone(x))) + normalize_ref(e.as_ref()).roll() } diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs index da52ba8..75e6e1d 100644 --- a/dhall/src/typecheck.rs +++ b/dhall/src/typecheck.rs @@ -187,7 +187,7 @@ pub fn type_with<S>( e: SubExpr<S, X>, ) -> Result<SubExpr<S, X>, TypeError<S>> where - S: ::std::fmt::Debug, + S: ::std::fmt::Debug + Clone, { use dhall_core::BinOp::*; use dhall_core::Builtin::*; @@ -453,7 +453,7 @@ pub fn normalized_type_with<S>( e: SubExpr<S, X>, ) -> Result<SubExpr<S, X>, TypeError<S>> where - S: ::std::fmt::Debug, + S: ::std::fmt::Debug + Clone, { Ok(normalize(type_with(ctx, e)?)) } @@ -461,7 +461,7 @@ where /// `typeOf` is the same as `type_with` with an empty context, meaning that the /// expression must be closed (i.e. no free variables), otherwise type-checking /// will fail. -pub fn type_of<S: ::std::fmt::Debug>( +pub fn type_of<S: ::std::fmt::Debug + Clone>( e: SubExpr<S, X>, ) -> Result<SubExpr<S, X>, TypeError<S>> { let ctx = Context::new(); |