Triangle - A bug or an extension?

exercises/practice/triangle/.docs/instructions.append.md

@@ -0,0 +1,6 @@
+# Instructions Append
+
+## Bonus: mixed types
+
+If you're up for it, there are a couple of bonus tests where the types of the arguments are not all the same.
+These tests are optional, so you don't _have_ to solve before submitting your solution.

exercises/practice/triangle/.meta/triangle.example.pl

@@ -1,14 +1,15 @@
-triangle(Side, Side, Side, "equilateral") :-
-    valid_triangle(Side, Side, Side), !.
+triangle(Side1, Side2, Side3, "equilateral") :-
+      Side1 =:= Side2,
+      Side2 =:= Side3,
+      valid_triangle(Side1, Side2, Side3).
 
-triangle(SideEq, SideEq, OtherSide, "isosceles") :-
-    valid_triangle(SideEq, SideEq, OtherSide), !.
-
-triangle(SideEq, OtherSide, SideEq, "isosceles") :-
-    valid_triangle(SideEq, SideEq, OtherSide), !.
-
-triangle(OtherSide, SideEq, SideEq, "isosceles") :-
-    valid_triangle(SideEq, SideEq, OtherSide), !.
+triangle(Side1, Side2, Side3, "isosceles") :-
+    (
+	Side1 =:= Side2
+    ;	Side1 =:= Side3
+    ;	Side2 =:= Side3
+    ),
+    valid_triangle(Side1, Side2, Side3).
 
 triangle(Side1, Side2, Side3, "scalene") :-
     \+ triangle(Side1, Side2, Side3, "equilateral"),
@@ -25,3 +26,4 @@
     Side1 \== 0,
     Side2 \== 0,
     Side3 \== 0.
+

exercises/practice/triangle/triangle_tests.plt

@@ -6,7 +6,7 @@ pending :-
 
 :- begin_tests(equilateral_triangle).
 
-    test(all_sides_are_equal, condition(true)) :-
+    test(all_sides_are_equal) :-
         triangle(2, 2, 2, "equilateral").
 
     test(any_side_is_unequal, [fail, condition(pending)]) :-
@@ -72,3 +72,21 @@ pending :-
         triangle((0.5), (0.4), (0.6), "scalene").
 
 :- end_tests(scalene_triangle).
+
+
+% BONUS TESTS
+bonus :-
+    current_prolog_flag(argv, ['--bonus'|_]).
+
+:- begin_tests(triangle_bonus, [condition(bonus)]).
+
+    test(all_sides_are_equal_but_mixed_types) :-
+        triangle(2, 2.0, 2, "equilateral").
+
+    test(sides_are_a_mix) :-
+        triangle(5, 4, 5.0, "isosceles").
+
+    test(no_sides_are_equal_mixed) :-
+        triangle(5.0, 4, 6, "scalene").
+
+:- end_tests(triangle_bonus).