From 8ce377d03357b68dbbcbe36d4c9a7607ccca0435 Mon Sep 17 00:00:00 2001
From: Mark Thom <markjordanthom@gmail.com>
Date: Sun, 19 Apr 2020 16:01:35 -0600
Subject: [PATCH] update toplevel comments, add mutable stack to zipped acyclic
 iterators

---
 src/prolog/heap_iter.rs                  | 22 +++++++++++++++++-----
 src/prolog/machine/machine_errors.rs     |  2 +-
 src/prolog/machine/machine_state_impl.rs |  3 ++-
 src/prolog/toplevel.pl                   |  5 ++++-
 4 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/src/prolog/heap_iter.rs b/src/prolog/heap_iter.rs
index 8a3ce492..1815ee19 100644
--- a/src/prolog/heap_iter.rs
+++ b/src/prolog/heap_iter.rs
@@ -120,10 +120,11 @@ impl<'a> Iterator for HCPreOrderIterator<'a> {
     }
 }
 
-pub trait MutStackHCIterator
-where Self: Iterator<Item = Addr>
+pub trait MutStackHCIterator<'b> where Self: Iterator
 {
-    fn stack(&mut self) -> &mut Vec<Addr>;
+    type MutStack;
+
+    fn stack(&'b mut self) -> Self::MutStack;
 }
 
 pub struct HCPostOrderIterator<'a> {
@@ -220,8 +221,10 @@ impl MachineState {
     }
 }
 
-impl<'a> MutStackHCIterator for HCPreOrderIterator<'a> {
-    fn stack(&mut self) -> &mut Vec<Addr> {
+impl<'b, 'a: 'b> MutStackHCIterator<'b> for HCPreOrderIterator<'a> {
+    type MutStack = &'b mut Vec<Addr>;
+
+    fn stack(&'b mut self) -> Self::MutStack {
         &mut self.state_stack
     }
 }
@@ -273,6 +276,14 @@ pub struct HCZippedAcyclicIterator<'a> {
     pub first_to_expire: Ordering,
 }
 
+impl<'b, 'a: 'b> MutStackHCIterator<'b> for HCZippedAcyclicIterator<'a> {
+    type MutStack = (&'b mut Vec<Addr>, &'b mut Vec<Addr>);
+
+    fn stack(&'b mut self) -> Self::MutStack {
+        (self.i1.stack(), self.i2.stack())
+    }
+}
+
 impl<'a> HCZippedAcyclicIterator<'a> {
     pub fn new(i1: HCPreOrderIterator<'a>, i2: HCPreOrderIterator<'a>) -> Self {
         HCZippedAcyclicIterator {
@@ -293,6 +304,7 @@ impl<'a> Iterator for HCZippedAcyclicIterator<'a>
             if !self.seen.contains(&(a1.clone(), a2.clone())) {
                 self.i1.stack().push(a1.clone());
                 self.i2.stack().push(a2.clone());
+
                 self.seen.insert((a1, a2));
 
                 break;
diff --git a/src/prolog/machine/machine_errors.rs b/src/prolog/machine/machine_errors.rs
index 68b7a3ff..9948787c 100644
--- a/src/prolog/machine/machine_errors.rs
+++ b/src/prolog/machine/machine_errors.rs
@@ -158,7 +158,7 @@ impl MachineError {
     pub(super)
     fn interrupt_error() -> Self {
         let stub = functor!("$interrupt_thrown");
-        
+
         MachineError {
             stub,
             location: None,
diff --git a/src/prolog/machine/machine_state_impl.rs b/src/prolog/machine/machine_state_impl.rs
index dfcb08be..188b3673 100644
--- a/src/prolog/machine/machine_state_impl.rs
+++ b/src/prolog/machine/machine_state_impl.rs
@@ -1969,7 +1969,8 @@ impl MachineState {
         iter.first_to_expire != Ordering::Equal
     }
 
-    pub(super) fn compare_term_test(&self, a1: &Addr, a2: &Addr) -> Option<Ordering> {
+    pub(super)
+    fn compare_term_test(&self, a1: &Addr, a2: &Addr) -> Option<Ordering> {
         let mut iter = self.zipped_acyclic_pre_order_iter(*a1, *a2);
 
         while let Some((v1, v2)) = iter.next() {
diff --git a/src/prolog/toplevel.pl b/src/prolog/toplevel.pl
index 099bc9f9..edd13ce0 100644
--- a/src/prolog/toplevel.pl
+++ b/src/prolog/toplevel.pl
@@ -214,7 +214,10 @@ gather_goals([Var = Value | Pairs], VarList, Goals) :-
     ).
 
 print_exception(E) :-
-    (  E == error('$interrupt_thrown', repl) -> nl % print the exception on a newline to evade "^C".
+    (  E == error('$interrupt_thrown', repl) -> nl % print the
+                                                   % exception on a
+                                                   % newline to evade
+                                                   % "^C".
     ;  true
     ),
     write_term('caught: ', [quoted(false), max_depth(20)]),
-- 
2.54.0