diff --git a/src/prolog/ast/arithmetic/Integer.kt b/src/prolog/ast/arithmetic/Integer.kt
index c12cfcd..96fd098 100644
--- a/src/prolog/ast/arithmetic/Integer.kt
+++ b/src/prolog/ast/arithmetic/Integer.kt
@@ -3,8 +3,9 @@ package prolog.ast.arithmetic
 import prolog.Answers
 import prolog.Substitutions
 import prolog.ast.logic.LogicOperand
+import prolog.ast.terms.Body
 
-data class Integer(override val value: Int) : Number, LogicOperand() {
+data class Integer(override val value: Int) : Number, Body, LogicOperand() {
     // Integers are already evaluated
     override fun simplify(subs: Substitutions): Simplification = Simplification(this, this)
 
diff --git a/src/prolog/ast/terms/Body.kt b/src/prolog/ast/terms/Body.kt
index 989c4d9..af78788 100644
--- a/src/prolog/ast/terms/Body.kt
+++ b/src/prolog/ast/terms/Body.kt
@@ -1,5 +1,8 @@
 package prolog.ast.terms
 
+import prolog.Substitutions
 import prolog.ast.logic.Satisfiable
 
-interface Body : Term, Satisfiable
+interface Body : Term, Satisfiable {
+    override fun applySubstitution(subs: Substitutions): Body
+}
diff --git a/src/prolog/builtins/arithmeticOperators.kt b/src/prolog/builtins/arithmeticOperators.kt
index dbdccf4..3a11979 100644
--- a/src/prolog/builtins/arithmeticOperators.kt
+++ b/src/prolog/builtins/arithmeticOperators.kt
@@ -40,8 +40,8 @@ class EvaluatesToDifferent(private val left: Expression, private val right: Expr
     }
 
     override fun applySubstitution(subs: Substitutions): EvaluatesToDifferent = EvaluatesToDifferent(
-        left.applySubstitution(subs) as Expression,
-        right.applySubstitution(subs) as Expression
+        applySubstitution(left, subs),
+        applySubstitution(right, subs)
     )
 }
 
@@ -63,8 +63,8 @@ class EvaluatesTo(private val left: Expression, private val right: Expression) :
     }
 
     override fun applySubstitution(subs: Substitutions): EvaluatesTo = EvaluatesTo(
-        left.applySubstitution(subs) as Expression,
-        right.applySubstitution(subs) as Expression
+        applySubstitution(left, subs),
+        applySubstitution(right, subs)
     )
 }
 
@@ -89,8 +89,8 @@ class Is(val number: Expression, val expr: Expression) :
     }
 
     override fun applySubstitution(subs: Substitutions): Is = Is(
-        number.applySubstitution(subs) as Expression,
-        expr.applySubstitution(subs) as Expression
+        applySubstitution(number, subs),
+        applySubstitution(expr, subs)
     )
 }
 
@@ -117,8 +117,8 @@ open class Add(private val expr1: Expression, private val expr2: Expression) :
     }
 
     override fun applySubstitution(subs: Substitutions): Add = Add(
-        expr1.applySubstitution(subs) as Expression,
-        expr2.applySubstitution(subs) as Expression
+        applySubstitution(expr1, subs),
+        applySubstitution(expr2, subs)
     )
 }
 
@@ -140,8 +140,8 @@ open class Subtract(private val expr1: Expression, private val expr2: Expression
     }
 
     override fun applySubstitution(subs: Substitutions): Subtract = Subtract(
-        expr1.applySubstitution(subs) as Expression,
-        expr2.applySubstitution(subs) as Expression
+        applySubstitution(expr1, subs),
+        applySubstitution(expr2, subs)
     )
 }
 
@@ -158,8 +158,8 @@ class Multiply(val expr1: Expression, val expr2: Expression) :
     }
 
     override fun applySubstitution(subs: Substitutions): Multiply = Multiply(
-        expr1.applySubstitution(subs) as Expression,
-        expr2.applySubstitution(subs) as Expression
+        applySubstitution(expr1, subs),
+        applySubstitution(expr2, subs)
     )
 }
 
@@ -173,8 +173,8 @@ class Divide(private val expr1: Expression, private val expr2: Expression) :
     }
 
     override fun applySubstitution(subs: Substitutions): Divide = Divide(
-        expr1.applySubstitution(subs) as Expression,
-        expr2.applySubstitution(subs) as Expression
+        applySubstitution(expr1, subs),
+        applySubstitution(expr2, subs)
     )
 }
 
@@ -206,9 +206,9 @@ class Between(private val expr1: Expression, private val expr2: Expression, priv
     }
 
     override fun applySubstitution(subs: Substitutions): Between = Between(
-        expr1.applySubstitution(subs) as Expression,
-        expr2.applySubstitution(subs) as Expression,
-        expr3.applySubstitution(subs) as Expression
+        applySubstitution(expr1, subs),
+        applySubstitution(expr2, subs),
+        applySubstitution(expr3, subs)
     )
 
     override fun toString(): String = "$expr1..$expr3..$expr2"
diff --git a/src/prolog/builtins/controlOperators.kt b/src/prolog/builtins/controlOperators.kt
index 3d81786..5fdcf80 100644
--- a/src/prolog/builtins/controlOperators.kt
+++ b/src/prolog/builtins/controlOperators.kt
@@ -55,7 +55,7 @@ open class Conjunction(val left: LogicOperand, private val right: LogicOperand)
                 right.fold(
                     // If the right part succeeds, yield the result with the left substitutions
                     onSuccess = { rightSubs ->
-                        yield(Result.success(leftSubs + rightSubs))
+                        yield(Result.success(rightSubs + leftSubs))
                     },
                     onFailure = { exception ->
                         // If the right part fails, check if it's a cut
@@ -74,8 +74,8 @@ open class Conjunction(val left: LogicOperand, private val right: LogicOperand)
         }
 
         fun findNextCutSolution(appliedCut: AppliedCut): Answers = sequence {
-            val leftSubs = appliedCut.subs
-            right.satisfy(subs + (appliedCut.subs!!)).firstOrNull()?.map { rightSubs ->
+            val leftSubs = appliedCut.subs ?: emptyMap()
+            right.satisfy(subs + leftSubs).firstOrNull()?.map { rightSubs ->
                 // If the right part succeeds, yield the result with the left substitutions
                 yield(Result.success(leftSubs + rightSubs))
                 return@sequence
diff --git a/tests/e2e/Examples.kt b/tests/e2e/Examples.kt
index 6df1df2..c6f7a51 100644
--- a/tests/e2e/Examples.kt
+++ b/tests/e2e/Examples.kt
@@ -27,7 +27,7 @@ class Examples {
 
     @Test
     fun debugHelper() {
-        loader.load("examples/meta/continuations.pl")
+        loader.load("examples/basics/summer.pl")
     }
 
     @ParameterizedTest
@@ -60,6 +60,7 @@ class Examples {
         Arguments.of("forall.pl", "Only alice likes pizza.\n"),
         Arguments.of("fraternity.pl", "Citizen robespierre is eligible for the event.\nCitizen danton is eligible for the event.\nCitizen camus is eligible for the event.\n"),
         Arguments.of("liberty.pl", "Give me Liberty, or give me Death!\nI disapprove of what you say, but I will defend to the death your right to say it.\nThe revolution devours its own children.\nSo this is how liberty dies, with thunderous applause.\n"),
+        Arguments.of("summer.pl", "rest(0)\nsum(4)\nrest(4)\nsum(7)\nrest(7)\nsum(9)\nrest(9)\nsum(10)\n"),
         Arguments.of("unification.pl", "While alice got an A, carol got an A, but bob did not get an A, dave did not get an A, unfortunately.\n"),
         Arguments.of("write.pl", "gpl zegt: dag(wereld)\n"),
     )