diff --git a/pom.xml b/pom.xml
index d473dad..c05f3ef 100644
--- a/pom.xml
+++ b/pom.xml
@@ -10,7 +10,7 @@
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <kotlin.version>1.2.30</kotlin.version>
+    <kotlin.version>1.2.31</kotlin.version>
     <junit5.version>5.1.0</junit5.version>
     <skipTests>false</skipTests>
   </properties>
diff --git a/src/main/kotlin/table/ExecutionContext.kt b/src/main/kotlin/table/ExecutionContext.kt
index 7b12b8e..aec7a42 100644
--- a/src/main/kotlin/table/ExecutionContext.kt
+++ b/src/main/kotlin/table/ExecutionContext.kt
@@ -15,14 +15,9 @@ object ExecutionContext {
     var isRecur: Boolean = false
         private set
 
-    val isInFunctionCall: Boolean
-        get() = !functionCalls.empty()
-
-    val currentFunction: LispFunction
-        get() = functionCalls.peek().lispFunction
-
-    val isRecurInitializing: Boolean
-        get() = functionCalls.peek().isRecurInitializing
+    fun isInFunctionCall() = !functionCalls.empty()
+    fun isRecurInitializing() = functionCalls.peek().isRecurInitializing
+    fun getCurrentFunction() = functionCalls.peek().lispFunction
 
     fun clearContext() {
         scope = SymbolTable(NullSymbolTable)
@@ -31,7 +26,7 @@ object ExecutionContext {
     }
 
     fun restoreGlobalScope() {
-        while (!scope.isGlobal)
+        while (!scope.isGlobal())
             scope = scope.parent ?: NullSymbolTable
     }
 
@@ -69,23 +64,14 @@ object ExecutionContext {
     }
 
     fun setRecurInitializing() {
-        functionCalls.peek().setRecurInitializing()
+        functionCalls.peek().isRecurInitializing = true
     }
 
     fun clearRecurInitializing() {
-        functionCalls.peek().clearRecurInitializing()
+        functionCalls.peek().isRecurInitializing = false
     }
 
-    class LispFunctionRecurInfo(val lispFunction: LispFunction) {
+    private class LispFunctionRecurInfo(val lispFunction: LispFunction) {
         var isRecurInitializing: Boolean = false
-            private set
-
-        fun setRecurInitializing() {
-            isRecurInitializing = true
-        }
-
-        fun clearRecurInitializing() {
-            isRecurInitializing = false
-        }
     }
 }
diff --git a/src/main/kotlin/table/SymbolTable.kt b/src/main/kotlin/table/SymbolTable.kt
index 9738758..fc5e51b 100644
--- a/src/main/kotlin/table/SymbolTable.kt
+++ b/src/main/kotlin/table/SymbolTable.kt
@@ -12,28 +12,22 @@ import kotlin.collections.Map.Entry
 
 open class SymbolTable @JvmOverloads constructor(open val parent: SymbolTable? = NullSymbolTable) : Iterable<SymbolTable> {
 
-    val isGlobal: Boolean
-        get() = parent === NullSymbolTable
-
     private val table: HashMap<String, SExpression> = HashMap()
 
-    private val sortedBindings: Set<Entry<String, SExpression>>
-        get() = TreeMap(table).entries
-
     override fun iterator(): Iterator<SymbolTable> = SymbolTableIterator(this)
-
-    operator fun contains(symbolName: String) = table.containsKey(symbolName)
-
+    operator fun contains(symbolName: String) = symbolName in table
     operator fun get(symbolName: String) = table[symbolName]
 
     operator fun set(symbolName: String, value: SExpression) {
         table[symbolName] = value
     }
 
+    fun isGlobal() = parent === NullSymbolTable
+
     fun toList(): Cons {
         var context: Cons = NIL
 
-        for (binding in sortedBindings)
+        for (binding in TreeMap(table).entries)
             context = append(context, makeList(makeSymbolValuePair(binding)))
 
         return context
@@ -43,11 +37,11 @@ open class SymbolTable @JvmOverloads constructor(open val parent: SymbolTable? =
         Cons(Symbol(binding.key), makeList(binding.value))
 
     object NullSymbolTable : SymbolTable(null) {
-        override val parent: SymbolTable
-            get() = this
+        override val parent = this
     }
 
     private class SymbolTableIterator(private var symbolTable: SymbolTable) : AbstractIterator<SymbolTable>() {
+
         override fun computeNext() {
             when (symbolTable) {
                 is NullSymbolTable -> done()
diff --git a/src/test/kotlin/table/ExecutionContextTest.kt b/src/test/kotlin/table/ExecutionContextTest.kt
index a4ded4f..84b06f8 100644
--- a/src/test/kotlin/table/ExecutionContextTest.kt
+++ b/src/test/kotlin/table/ExecutionContextTest.kt
@@ -92,9 +92,9 @@ class ExecutionContextTest {
         val scope3 = SymbolTable(scope2)
         executionContext.scope = scope3
 
-        assertThat(executionContext.scope.isGlobal).isFalse()
+        assertThat(executionContext.scope.isGlobal()).isFalse()
         executionContext.restoreGlobalScope()
-        assertThat(executionContext.scope.isGlobal).isTrue()
+        assertThat(executionContext.scope.isGlobal()).isTrue()
         assertThat(executionContext.scope).isEqualTo(global)
     }
 }
diff --git a/src/test/kotlin/table/FunctionTableTest.kt b/src/test/kotlin/table/FunctionTableTest.kt
index 27ec5dd..acab1dd 100644
--- a/src/test/kotlin/table/FunctionTableTest.kt
+++ b/src/test/kotlin/table/FunctionTableTest.kt
@@ -11,6 +11,7 @@ import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.TestInstance
 import org.junit.jupiter.api.TestInstance.Lifecycle.PER_CLASS
 import sexpression.Cons
+import sexpression.LispString
 import sexpression.Nil
 import sexpression.Nil.NIL
 import sexpression.Symbol.T
@@ -25,8 +26,8 @@ import java.util.HashSet
 class FunctionTableTest {
 
     @FunctionNames("GOOD")
-    class GoodFunction(name: String) : LispFunction() {
-        override fun call(argumentList: Cons): Nil = NIL
+    class GoodFunction(private val name: String) : LispFunction() {
+        override fun call(argumentList: Cons): LispString = LispString(name)
     }
 
     @FunctionNames("BAD")