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-rw-r--r--dhall/src/normalize.rs18
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(),