1 files changed, 24 insertions, 0 deletions
diff --git a/prolog/problems/denotational_semantics/prog_listswap_3/common.py b/prolog/problems/denotational_semantics/prog_listswap_3/common.py
new file mode 100644
index 0000000..110890d
--- /dev/null
+++ b/prolog/problems/denotational_semantics/prog_listswap_3/common.py
@@ -0,0 +1,24 @@
+id = 174
+group = 'denotational_semantics'
+number = 80
+visible = True
+facts = 'denotational_semantics_aux__predicates'
+
+solution = '''\
+prog_listswap(In-->Out) -->
+    [begin], instructs174((In,1)-->(Out,_)), [end].
+
+instructs174((R0,C0)-->(R,C)) -->
+    instr174((R0,C0)-->(R,C)).
+instructs174((R0,C0)-->(R,C)) -->
+    instr174((R0,C0)-->(R1,C1)),
+    instructs174((R1,C1)-->(R,C)).
+
+instr174((R0,C0)-->(R0,C)) -->
+    [left], { C0 > 1, C is C0 - 1 ; C0 =< 1, C is C0 }.
+instr174((R0,C0)-->(R0,C)) -->
+  [right], { length(R0, LenR0),
+            ( C0 < LenR0, C is C0 + 1 ; C0 >= LenR0, C is C0 ) }.
+
+instr174((R0,C0)-->(R,C0)) -->
+  [swap], {swap(R0,C0,R)}.'''