diff --git a/include/yaml-cpp/emitter.h b/include/yaml-cpp/emitter.h
index 210b1ec97..c6190a2b6 100644
--- a/include/yaml-cpp/emitter.h
+++ b/include/yaml-cpp/emitter.h
@@ -44,7 +44,7 @@ class YAML_CPP_API Emitter {
 
   // state checking
   bool good() const;
-  const std::string GetLastError() const;
+  std::string GetLastError() const;
 
   // global setters
   bool SetOutputCharset(EMITTER_MANIP value);
@@ -126,7 +126,6 @@ class YAML_CPP_API Emitter {
 
   const char* ComputeFullBoolName(bool b) const;
   const char* ComputeNullName() const;
-  bool CanEmitNewline() const;
 
  private:
   std::unique_ptr<EmitterState> m_pState;
diff --git a/src/directives.cpp b/src/directives.cpp
index f6e9587c6..4b8227078 100644
--- a/src/directives.cpp
+++ b/src/directives.cpp
@@ -3,8 +3,7 @@
 namespace YAML {
 Directives::Directives() : version{true, 1, 2}, tags{} {}
 
-const std::string Directives::TranslateTagHandle(
-    const std::string& handle) const {
+std::string Directives::TranslateTagHandle(const std::string& handle) const {
   auto it = tags.find(handle);
   if (it == tags.end()) {
     if (handle == "!!")
diff --git a/src/directives.h b/src/directives.h
index 333af26e3..18d14c9c0 100644
--- a/src/directives.h
+++ b/src/directives.h
@@ -19,7 +19,7 @@ struct Version {
 struct Directives {
   Directives();
 
-  const std::string TranslateTagHandle(const std::string& handle) const;
+  std::string TranslateTagHandle(const std::string& handle) const;
 
   Version version;
   std::map<std::string, std::string> tags;
diff --git a/src/emitter.cpp b/src/emitter.cpp
index 644b3129b..46f656b2b 100644
--- a/src/emitter.cpp
+++ b/src/emitter.cpp
@@ -25,9 +25,7 @@ std::size_t Emitter::size() const { return m_stream.pos(); }
 // state checking
 bool Emitter::good() const { return m_pState->good(); }
 
-const std::string Emitter::GetLastError() const {
-  return m_pState->GetLastError();
-}
+std::string Emitter::GetLastError() const { return m_pState->GetLastError(); }
 
 // global setters
 bool Emitter::SetOutputCharset(EMITTER_MANIP value) {
@@ -271,8 +269,6 @@ void Emitter::EmitNewline() {
   m_pState->SetNonContent();
 }
 
-bool Emitter::CanEmitNewline() const { return true; }
-
 // Put the stream in a state so we can simply write the next node
 // E.g., if we're in a sequence, write the "- "
 void Emitter::PrepareNode(EmitterNodeType::value child) {
diff --git a/src/scanner.cpp b/src/scanner.cpp
index ea5511a11..2f858c05f 100644
--- a/src/scanner.cpp
+++ b/src/scanner.cpp
@@ -7,6 +7,19 @@
 #include "yaml-cpp/exceptions.h"  // IWYU pragma: keep
 
 namespace YAML {
+namespace {
+// IsWhitespaceToBeEaten
+// . We can eat whitespace if it's a space or tab
+// . Note: originally tabs in block context couldn't be eaten
+//         "where a simple key could be allowed
+//         (i.e., not at the beginning of a line, or following '-', '?', or
+// ':')"
+//   I think this is wrong, since tabs can be non-content whitespace; it's just
+//   that they can't contribute to indentation, so once you've seen a tab in a
+//   line, you can't start a simple key
+bool IsWhitespaceToBeEaten(char ch) { return (ch == ' ') || (ch == '\t'); }
+}  // namespace
+
 Scanner::Scanner(std::istream& in)
     : INPUT(in),
       m_tokens{},
@@ -213,27 +226,6 @@ void Scanner::ScanToNextToken() {
 ///////////////////////////////////////////////////////////////////////
 // Misc. helpers
 
-// IsWhitespaceToBeEaten
-// . We can eat whitespace if it's a space or tab
-// . Note: originally tabs in block context couldn't be eaten
-//         "where a simple key could be allowed
-//         (i.e., not at the beginning of a line, or following '-', '?', or
-// ':')"
-//   I think this is wrong, since tabs can be non-content whitespace; it's just
-//   that they can't contribute to indentation, so once you've seen a tab in a
-//   line, you can't start a simple key
-bool Scanner::IsWhitespaceToBeEaten(char ch) {
-  if (ch == ' ') {
-    return true;
-  }
-
-  if (ch == '\t') {
-    return true;
-  }
-
-  return false;
-}
-
 const RegEx& Scanner::GetValueRegex() const {
   if (InBlockContext()) {
     return Exp::Value();
@@ -269,7 +261,7 @@ Token* Scanner::PushToken(Token::TYPE type) {
   return &m_tokens.back();
 }
 
-Token::TYPE Scanner::GetStartTokenFor(IndentMarker::INDENT_TYPE type) const {
+Token::TYPE Scanner::GetStartTokenFor(IndentMarker::INDENT_TYPE type) {
   switch (type) {
     case IndentMarker::SEQ:
       return Token::BLOCK_SEQ_START;
diff --git a/src/scanner.h b/src/scanner.h
index c653ac69f..8f33d1609 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -90,7 +90,7 @@ class Scanner {
   bool InBlockContext() const { return m_flows.empty(); }
   std::size_t GetFlowLevel() const { return m_flows.size(); }
 
-  Token::TYPE GetStartTokenFor(IndentMarker::INDENT_TYPE type) const;
+  static Token::TYPE GetStartTokenFor(IndentMarker::INDENT_TYPE type);
 
   /**
    * Pushes an indentation onto the stack, and enqueues the proper token
@@ -131,8 +131,6 @@ class Scanner {
    */
   void ThrowParserException(const std::string &msg) const;
 
-  bool IsWhitespaceToBeEaten(char ch);
-
   /**
    * Returns the appropriate regex to check if the next token is a value token.
    */
diff --git a/src/scantag.cpp b/src/scantag.cpp
index 176cc5c71..63bc1e537 100644
--- a/src/scantag.cpp
+++ b/src/scantag.cpp
@@ -6,7 +6,7 @@
 #include "yaml-cpp/mark.h"
 
 namespace YAML {
-const std::string ScanVerbatimTag(Stream& INPUT) {
+std::string ScanVerbatimTag(Stream& INPUT) {
   std::string tag;
 
   // eat the start character
@@ -29,7 +29,7 @@ const std::string ScanVerbatimTag(Stream& INPUT) {
   throw ParserException(INPUT.mark(), ErrorMsg::END_OF_VERBATIM_TAG);
 }
 
-const std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle) {
+std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle) {
   std::string tag;
   canBeHandle = true;
   Mark firstNonWordChar;
@@ -62,7 +62,7 @@ const std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle) {
   return tag;
 }
 
-const std::string ScanTagSuffix(Stream& INPUT) {
+std::string ScanTagSuffix(Stream& INPUT) {
   std::string tag;
 
   while (INPUT) {
diff --git a/src/scantag.h b/src/scantag.h
index 522ba5495..9fa1684dc 100644
--- a/src/scantag.h
+++ b/src/scantag.h
@@ -11,9 +11,9 @@
 #include "stream.h"
 
 namespace YAML {
-const std::string ScanVerbatimTag(Stream& INPUT);
-const std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle);
-const std::string ScanTagSuffix(Stream& INPUT);
+std::string ScanVerbatimTag(Stream& INPUT);
+std::string ScanTagHandle(Stream& INPUT, bool& canBeHandle);
+std::string ScanTagSuffix(Stream& INPUT);
 }
 
 #endif  // SCANTAG_H_62B23520_7C8E_11DE_8A39_0800200C9A66
diff --git a/src/singledocparser.cpp b/src/singledocparser.cpp
index 405ecade1..1a6f1af6f 100644
--- a/src/singledocparser.cpp
+++ b/src/singledocparser.cpp
@@ -93,9 +93,9 @@ void SingleDocParser::HandleNode(EventHandler& eventHandler) {
   // add non-specific tags
   if (tag.empty())
     tag = (token.type == Token::NON_PLAIN_SCALAR ? "!" : "?");
-  
-  if (token.type == Token::PLAIN_SCALAR 
-      && tag.compare("?") == 0 && IsNullString(token.value)) {
+
+  if (token.type == Token::PLAIN_SCALAR && tag == "?" &&
+      IsNullString(token.value)) {
     eventHandler.OnNull(mark, anchor);
     m_scanner.pop();
     return;
diff --git a/src/tag.cpp b/src/tag.cpp
index df8a2cf46..9d36317de 100644
--- a/src/tag.cpp
+++ b/src/tag.cpp
@@ -29,7 +29,7 @@ Tag::Tag(const Token& token)
   }
 }
 
-const std::string Tag::Translate(const Directives& directives) {
+std::string Tag::Translate(const Directives& directives) const {
   switch (type) {
     case VERBATIM:
       return value;
diff --git a/src/tag.h b/src/tag.h
index ac30673b9..efa77f0fb 100644
--- a/src/tag.h
+++ b/src/tag.h
@@ -23,7 +23,7 @@ struct Tag {
   };
 
   Tag(const Token& token);
-  const std::string Translate(const Directives& directives);
+  std::string Translate(const Directives& directives) const;
 
   TYPE type;
   std::string handle, value;