correct copier.

src/prolog/copier.rs

@@ -3,20 +3,12 @@ use prolog::instructions::*;
 
 use std::ops::IndexMut;
 
-//type ListTrail = HashMap<usize, usize>;
 type Trail = Vec<(Ref, HeapCellValue)>;
 
 pub(crate) struct RedirectInfo {
-    //list_trail: ListTrail,
     trail: Trail
 }
-/*
+
-impl RedirectInfo {
-    fn new() -> Self {
-        RedirectInfo { list_trail: ListTrail::new(), trail: Trail::new() }
-    }
-}
-*/
 pub(crate) trait CopierTarget
 {
     fn source(&self) -> usize;
@@ -59,7 +51,6 @@ pub(crate) trait CopierTarget
     fn duplicate_term_impl(&mut self, addr: Addr) -> RedirectInfo
       where Self: IndexMut<usize, Output=HeapCellValue>
     {
-        // let mut redirect_info = RedirectInfo::new();
         let mut trail = Trail::new();
         let mut scan = self.source();
         let old_h = self.threshold();

src/prolog/heap_iter.rs

@@ -60,10 +60,8 @@ impl<'a> HCPreOrderIterator<'a> {
 
                 da
             },
-            Addr::HeapCell(_) | Addr::StackCell(_, _) =>
+            Addr::HeapCell(_) | Addr::StackCell(_, _) => da,
-                da,
+            Addr::Str(s) => self.follow_heap(s) // record terms of structure.
-            Addr::Str(s) =>
-                self.follow_heap(s) // record terms of structure.
         }
     }
 }