diff options
| -rw-r--r-- | dhall/src/normalize.rs | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs index 3c04b9e..bf1bff5 100644 --- a/dhall/src/normalize.rs +++ b/dhall/src/normalize.rs @@ -4,7 +4,7 @@ use dhall_generator::dhall_expr; use std::fmt; use std::rc::Rc; -fn apply_builtin<S, A>(b: Builtin, args: Vec<SubExpr<S, A>>) -> SubExpr<S, A> +fn apply_builtin<S, A>(b: Builtin, mut args: Vec<SubExpr<S, A>>) -> SubExpr<S, A> where S: fmt::Debug, A: fmt::Debug, @@ -13,8 +13,8 @@ where use dhall_core::Builtin::*; use dhall_core::Expr::*; let f = rc(Builtin(b)); - // How many arguments for each builtin, and which argument - // is the important one for pattern-matching + // 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), @@ -35,10 +35,11 @@ where NaturalFold => (1, Some(0)), _ => (0, None), }; - let mut args = args.to_vec(); + // 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] = Rc::clone(&normalize_whnf(&args[i])); } @@ -79,6 +80,7 @@ where }; let a0 = Rc::clone(a0); 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)); } } @@ -93,6 +95,7 @@ where } }; let a0 = Rc::clone(a0); + // TODO: use Embed to avoid reevaluating g break dhall_expr!((g (Optional a0)) (λ(x: a0) -> [x] : Optional a0) ([] : Optional a0)); } } @@ -146,6 +149,9 @@ where } _ => return rc(App(f, args)), }; + // 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(Expr::App(ret, args.split_off(len_consumption)))) } @@ -165,7 +171,10 @@ where Let(f, _, r, b) => { let vf0 = &V(f.clone(), 0); let r2 = shift(1, vf0, r); + // TODO: use a context let b2 = subst(vf0, &r2, b); + // TODO: add tests sensitive to shift errors before + // trying anything let b3 = shift(-1, vf0, &b2); normalize_whnf(&b3) } @@ -175,6 +184,7 @@ where 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(), |