From 6e20f82d6fbff17608eea313784bb3666cecfed4 Mon Sep 17 00:00:00 2001
From: Mark Thom <markjordanthom@gmail.com>
Date: Thu, 15 Nov 2018 23:04:52 -0700
Subject: [PATCH] fix faulty tidy_trail

---
 src/prolog/lib/dcgs.pl                   | 4 ++--
 src/prolog/machine/machine_state_impl.rs | 8 +++++---
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/prolog/lib/dcgs.pl b/src/prolog/lib/dcgs.pl
index e3ac00a0..d92e6d2b 100644
--- a/src/prolog/lib/dcgs.pl
+++ b/src/prolog/lib/dcgs.pl
@@ -6,7 +6,7 @@
 :- op(1200, xfx, -->).
 
 phrase(G, G) :-
-    nonvar(G), G = [_|_], !. %, append(G, _, Ls0).
+    nonvar(G), G = [_|_], !.
 phrase(G, Ls0) :-
     nonvar(G), G = (G1, G2), !, phrase(G1, Ls0, Ls1), phrase(G2, Ls1, []).
 phrase(G, Ls0) :-
@@ -50,7 +50,7 @@ expand_body(Term0, (ModTerm, ModTerms), N0, N) :-
     nonvar(Term),
     expand_body_term(Term, ModTerm, N0, N1),
     expand_body(Terms, ModTerms, N1, N).
-expand_body(Term0, ModTerm, N0, N) :-    
+expand_body(Term0, ModTerm, N0, N) :-
     nonvar(Term0),
     expand_body_term(Term0, ModTerm, N0, N).
 
diff --git a/src/prolog/machine/machine_state_impl.rs b/src/prolog/machine/machine_state_impl.rs
index 851e9800..d479d2e0 100644
--- a/src/prolog/machine/machine_state_impl.rs
+++ b/src/prolog/machine/machine_state_impl.rs
@@ -32,7 +32,7 @@ macro_rules! try_or_fail {
 
 impl MachineState {
     pub(super) fn new() -> Self {
-        MachineState {            
+        MachineState {
             s: 0,
             p: CodePtr::default(),
             b: 0,
@@ -132,10 +132,10 @@ impl MachineState {
         output.append(" = ");
 
         let mut printer = HCPrinter::from_heap_locs(&self, output, var_dir);
-        
+
         printer.numbervars = false;
         printer.quoted = true;
-            
+
         let mut output = printer.print(addr);
 
         let bad_ending = format!("= {}", &var);
@@ -428,6 +428,7 @@ impl MachineState {
                         let tr = self.tr;
                         let val = self.trail[tr - 1];
                         self.trail[i] = val;
+                        self.trail.pop();
                         self.tr -= 1;
                     },
                 Ref::StackCell(fr, _) => {
@@ -445,6 +446,7 @@ impl MachineState {
                         let tr = self.tr;
                         let val = self.trail[tr - 1];
                         self.trail[i] = val;
+                        self.trail.pop();
                         self.tr -= 1;
                     }
                 }
-- 
2.54.0