Triangle - A bug or an extension?

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

@@ -0,0 +1,22 @@
+# Instructions Append
+
+## Type equality not enforced
+
+### Before
+
+Tests didn't test for the situation in which parameters weren't of the same ***type***.
+
+### Implication
+
+A solution with ***strict type equality*** would be **passing**.
+
+Example(of a solution enforcing type equality):
+```prolog
+?- triangle(1.0, 1, 1).
+false
+```
+
+### Currently
+
+A solution which doesn't enforce type equality is required.
+The above example would necessarily be ***true***, for a solution passing the tests.

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

@@ -21,6 +21,9 @@ pending :-
     test(all_sides_are_floats_and_equal, condition(pending)) :-
         triangle((0.5), (0.5), (0.5), "equilateral").
 
+    test(all_sides_are_equal_but_mixed_types, condition(true)) :-
+        triangle(2, 2.0, 2, "equilateral").
+
 :- end_tests(equilateral_triangle).
 
 :- begin_tests(isosceles_triangle).
@@ -52,6 +55,9 @@ pending :-
     test(sides_may_be_floats, condition(pending)) :-
         triangle((0.5), (0.4), (0.5), "isosceles").
 
+    test(sides_are_a_mix, condition(pending)) :-
+        triangle(5, 4, 5.0, "isosceles").
+
 :- end_tests(isosceles_triangle).
 
 :- begin_tests(scalene_triangle).