Remove redundant match_result_product() function

Author: vsbogd

lib/examples/custom_match.rs

@@ -36,14 +36,15 @@ impl Grounded for TestDict {
 impl CustomMatch for TestDict {
     fn match_(&self, other: &Atom) -> MatchResultIter {
         if let Some(other) = other.as_gnd::<TestDict>() {
-            other.0.iter().map(|(ko, vo)| {
+            Box::new(other.0.iter().map(|(ko, vo)| {
                 self.0.iter().map(|(k, v)| {
                     match_atoms(&Atom::expr(vec![k.clone(), v.clone()]), &Atom::expr(vec![ko.clone(), vo.clone()]))
                 }).fold(Box::new(std::iter::empty()) as MatchResultIter, |acc, i| {
                     Box::new(acc.chain(i))
-                })
-            }).fold(Box::new(std::iter::once(Bindings::new())),
-            |acc, i| { matcher::match_result_product(acc, i) })
+                }).collect::<BindingsSet>()
+            }).fold(BindingsSet::single(),
+            |acc, i| { acc.merge(&i) })
+            .into_iter())
         } else {
             Box::new(std::iter::empty())
         }

lib/src/atom/matcher.rs

@@ -1134,16 +1134,6 @@ fn match_atoms_recursively(left: &Atom, right: &Atom) -> BindingsSet {
     res
 }
 
-//TODO: This function is redundant, as the functionality is subsumed by BindingsSet::merge
-/// Merges each bindings from `prev` iter to each bindings from `next`
-/// iter. The result is an iter over successfully merged bindings.
-pub fn match_result_product(prev: MatchResultIter, next: MatchResultIter) -> MatchResultIter {
-    let next: BindingsSet = next.collect();
-    let prev: BindingsSet = prev.collect();
-    log::trace!("match_result_product_iter, next: {:?}", next);
-    Box::new(prev.merge(&next).into_iter())
-}
-
 /// Applies bindings to atom and return it (see [apply_bindings_to_atom_mut]).
 #[inline]
 pub fn apply_bindings_to_atom_move(mut atom: Atom, bindings: &Bindings) -> Atom {