executor, mostly

src/executor/partial_hash.rs

@@ -0,0 +1,38 @@
+use std::hash::{Hasher, Hash};
+
+use super::super::representations::typed::{Clause, Expr};
+use super::super::utils::Stackframe;
+
+/// Hash the parts of an expression that are required to be equal for syntactic equality.
+pub fn partial_hash_rec<H: Hasher>(Expr(clause, _): &Expr, state: &mut H, is_auto: Stackframe<bool>) {
+    match clause {
+        // Skip autos and explicits
+        Clause::Auto(_, body) => partial_hash_rec(body, state, is_auto.push(true)),
+        Clause::Explicit(f, _) => partial_hash_rec(f, state, is_auto),
+        // Annotate everything else with a prefix
+        // - Recurse into the tree of lambdas and calls - classic lambda calc
+        Clause::Lambda(_, body) => {
+            state.write_u8(0);
+            partial_hash_rec(body, state, is_auto.push(false))
+        }
+        Clause::Apply(f, x) => {
+            state.write_u8(1);
+            partial_hash_rec(f, state, is_auto);
+            partial_hash_rec(x, state, is_auto);
+        }
+        // - Only recognize the depth of an argument if it refers to a non-auto parameter
+        Clause::Argument(depth) => {
+            // If the argument references an auto, acknowledge its existence
+            if *is_auto.iter().nth(*depth).unwrap_or(&false) {
+                state.write_u8(2)
+            } else {
+                state.write_u8(3);
+                state.write_usize(*depth)
+            }
+        }
+        // - Hash leaves like normal
+        Clause::Literal(lit) => { state.write_u8(4); lit.hash(state) }
+        Clause::Atom(at) => { state.write_u8(5); at.hash(state) }
+        Clause::ExternFn(f) => { state.write_u8(6); f.hash(state) }
+    }
+}