add (\=)/2.

README.md

@@ -85,6 +85,7 @@ The following predicates are built-in to rusty-wam.
 * `(==)/2`
 * `(\==)/2`
 * `(=)/2`
+* `(\=)/2`
 * `(=..)/2`
 * `(->)/2`
 * `(;)/2`

src/main.rs

@@ -6,6 +6,7 @@ mod prolog;
 #[macro_use] mod test_utils;
 
 use prolog::io::*;
+use prolog::lib::control::*;
 use prolog::lib::lists::*;
 use prolog::machine::*;
 
@@ -35,6 +36,7 @@ fn prolog_repl() {
     let mut wam = Machine::new();
 
     load_init_str(&mut wam, LISTS);
+    load_init_str(&mut wam, CONTROL);
     
     loop {
         print!("prolog> ");

src/prolog/ast.rs

@@ -391,12 +391,12 @@ impl CompareNumberQT {
 
 #[derive(Clone, Copy)]
 pub enum CompareTermQT {    
-    GreaterThan,
     LessThan,
-    GreaterThanOrEqual,
     LessThanOrEqual,
+    Equal,
+    GreaterThanOrEqual,
+    GreaterThan,        
     NotEqual,    
-    Equal
 }
 
 impl CompareTermQT {

src/prolog/lib/control.rs

@@ -0,0 +1,13 @@
+pub static CONTROL: &str = ":- op(700, xfx, \\=).
+
+                            once(G) :- G, !.
+
+                            \\=(X, X) :- !, false.
+                            \\=(_, _).
+
+                            between(Lower, Upper, Lower) :-
+                               Lower =< Upper.
+                            between(Lower1, Upper, X) :-
+                               Lower1 < Upper,
+                               Lower2 is Lower1 + 1,
+                               between(Lower2, Upper, X).";

src/prolog/lib/lists.rs

@@ -7,23 +7,14 @@ pub static LISTS: &str = "member(X, [X|_]).
                           append([], R, R).
                           append([X|L], R, [X|S]) :- append(L, R, S).
 
-                          once(G) :- G, !.
-                          
                           memberchk(X, Xs) :- member(X, Xs), !.
 
                           reverse(Xs, Ys) :- reverse(Xs, [], Ys).
 
-                          reverse([], Ys, Ys) :- !.
+                          reverse([], Ys, Ys).
                           reverse([H|T], Ps, Rs) :-
                               reverse(T, [H|Ps], Rs).
 
-                          between(Lower, Upper, Lower) :-
-                             Lower =< Upper.
-                          between(Lower1, Upper, X) :-
-                             Lower1 < Upper,
-                             Lower2 is Lower1 + 1,
-                             between(Lower2, Upper, X).
-                          
                           maplist(_, []).
                           maplist(Cont1, [E1|E1s]) :-
                              call(Cont1, E1),

src/prolog/lib/mod.rs

@@ -1 +1,3 @@
+pub mod control;
 pub mod lists;
+