diff --git a/src/main/kotlin/scanner/LispCommentRemovingInputStream.kt b/src/main/kotlin/scanner/LispCommentRemovingInputStream.kt
index 7730058..18ec9e4 100644
--- a/src/main/kotlin/scanner/LispCommentRemovingInputStream.kt
+++ b/src/main/kotlin/scanner/LispCommentRemovingInputStream.kt
@@ -11,7 +11,7 @@ import java.io.InputStream
 /**
  * Removes Lisp comments from an input stream.
  */
-class LispCommentRemovingInputStream(underlyingInputStream: InputStream) : LispInputStream {
+class LispCommentRemovingInputStream(underlyingInputStream: InputStream) : LispInputStream() {
 
     private val underlyingInputStream = SafeInputStream(underlyingInputStream)
     private var isInQuotedString = false
@@ -19,6 +19,10 @@ class LispCommentRemovingInputStream(underlyingInputStream: InputStream) : LispI
     private var previousCharacter = 0
     private var currentCharacter = 0
 
+    override fun computeNext() = read().let {
+        if (it == EOF) done() else setNext(it)
+    }
+
     override fun read(): Int {
         if (!rereadLastCharacter)
             return readFromUnderlyingInputStream()
diff --git a/src/main/kotlin/scanner/LispInputStream.kt b/src/main/kotlin/scanner/LispInputStream.kt
index 24ac439..e0fe1ba 100644
--- a/src/main/kotlin/scanner/LispInputStream.kt
+++ b/src/main/kotlin/scanner/LispInputStream.kt
@@ -2,10 +2,10 @@ package scanner
 
 import error.CriticalLispException
 
-interface LispInputStream {
+abstract class LispInputStream: AbstractIterator<Int>() {
 
-    fun read(): Int
-    fun unreadLastCharacter()
+    abstract fun read(): Int
+    abstract fun unreadLastCharacter()
 
     class MaximumUnreadsExceededException : CriticalLispException()
 }
diff --git a/src/main/kotlin/scanner/LispScanner.kt b/src/main/kotlin/scanner/LispScanner.kt
index 489f154..7210aac 100644
--- a/src/main/kotlin/scanner/LispScanner.kt
+++ b/src/main/kotlin/scanner/LispScanner.kt
@@ -27,8 +27,7 @@ class LispScanner(inputStream: InputStream, fileName: String) {
 
     val nextToken: Token
         get() {
-            var c = inputStream.read()
-            while (c != EOF) {
+            for (c in inputStream) {
                 val currentCharacter = c.toChar()
                 positionTracker.incrementColumn()
 
@@ -36,8 +35,6 @@ class LispScanner(inputStream: InputStream, fileName: String) {
                     return createTokenFromCharacter(currentCharacter)
                 else if (currentCharacter == NEWLINE)
                     positionTracker.incrementLine()
-
-                c = inputStream.read()
             }
 
             return tokenFactory.createEofToken(positionTracker.currentPosition())
@@ -64,7 +61,7 @@ class LispScanner(inputStream: InputStream, fileName: String) {
         val nextCharacter = inputStream.read().toChar()
         inputStream.unreadLastCharacter()
 
-        return if (isDigit(nextCharacter))
+        return if (nextCharacter.isDigit())
             retrieveNumberTokenText(firstCharacter)
         else
             retrieveIdentifierTokenText(firstCharacter)
@@ -79,12 +76,12 @@ class LispScanner(inputStream: InputStream, fileName: String) {
     private fun retrieveIdentifierTokenText(firstCharacter: Char) =
         ComplexTokenTextRetriever(firstCharacter, Characters::isIdentifierCharacter).retrieveToken()
 
-    private inner class ComplexTokenTextRetriever(internal var firstCharacter: Char,
-                                                  internal var isPartOfToken: (Char) -> Boolean) {
-        internal var text = StringBuilder()
-        internal var position = positionTracker.currentPosition()
-        internal var currentCharacter = firstCharacter
-        internal var previousCharacter = firstCharacter
+    private inner class ComplexTokenTextRetriever(private val firstCharacter: Char,
+                                                  private val isPartOfToken: (Char) -> Boolean) {
+        private val text = StringBuilder()
+        private val position = positionTracker.currentPosition()
+        private var currentCharacter = firstCharacter
+        private var previousCharacter = firstCharacter
 
         private fun isTerminatingCharacter() = isStringToken() && isTerminatingDoubleQuote()
         private fun isStringToken() = firstCharacter == DOUBLE_QUOTE
@@ -93,8 +90,7 @@ class LispScanner(inputStream: InputStream, fileName: String) {
         fun retrieveToken(): String {
             text.append(firstCharacter)
 
-            var c = inputStream.read()
-            while (c != EOF) {
+            for (c in inputStream) {
                 currentCharacter = c.toChar()
 
                 if (!isPartOfToken(currentCharacter)) {
@@ -109,7 +105,6 @@ class LispScanner(inputStream: InputStream, fileName: String) {
                     return text.toString()
 
                 previousCharacter = currentCharacter
-                c = inputStream.read()
             }
 
             return terminateTokenWithEof()
diff --git a/src/main/kotlin/util/Characters.kt b/src/main/kotlin/util/Characters.kt
index 8ed4b38..40dabb0 100644
--- a/src/main/kotlin/util/Characters.kt
+++ b/src/main/kotlin/util/Characters.kt
@@ -43,6 +43,5 @@ object Characters {
     }
 
     fun isIdentifierCharacter(c: Char) = !Character.isWhitespace(c) && !illegalIdentifierCharacters.contains(c)
-    fun isLegalStringCharacter(c: Char) = true
     fun isNumberPrefix(c: Char) = c == DASH || c == PLUS
 }