diff --git a/example/tokenrepl/tokenrepl.cpp b/example/tokenrepl/tokenrepl.cpp
index 9afe0059..d6eacfea 100644
--- a/example/tokenrepl/tokenrepl.cpp
+++ b/example/tokenrepl/tokenrepl.cpp
@@ -41,7 +41,7 @@ main() {
             if (tk.is_valid()) {
                 cout << tk << endl;
             } else if (error.is_error()) {
-                cout << "parsing error: " << endl;
+                cout << "tokenizer error: " << endl;
                 error.report(cout);
 
                 break;
diff --git a/include/xo/tokenizer/span.hpp b/include/xo/tokenizer/span.hpp
index bb1eeccb..8cf7a4a7 100644
--- a/include/xo/tokenizer/span.hpp
+++ b/include/xo/tokenizer/span.hpp
@@ -104,6 +104,18 @@ namespace xo {
             /** @defgroup span-general-methods **/
             ///@{
 
+            /** @brief strip prefix until first occurence of '\n', including the newline **/
+            void discard_until_newline() {
+                for (const CharT * p = lo_; p < hi_; ++p) {
+                    if (*p == '\n') {
+                        lo_ = p + 1;
+                        return;
+                    }
+                }
+
+                lo_ = hi_;
+            }
+
             /** Create new span over supplied type,
              *  with identical (possibly misaligned) endpoints.
              *
@@ -142,8 +154,7 @@ namespace xo {
 
             /** @brief create span with @p prefix of this span removed **/
             span after_prefix(const span & prefix) const {
-                assert(prefix.lo() == lo_);
-                if (prefix.lo() != lo_) {
+                if (!prefix.is_null() && (prefix.lo() != lo_)) {
                     throw std::runtime_error
                         ("after_prefix: expected prefix of this span");
                 }
@@ -174,7 +185,7 @@ namespace xo {
             span & operator+=(const span & x) {
                 if (hi_ == x.lo_) {
                     hi_ = x.hi_;
-                } else {
+                } else if (!x.is_null()) {
                     assert(false);
                 }
 
diff --git a/include/xo/tokenizer/tokenizer.hpp b/include/xo/tokenizer/tokenizer.hpp
index 75e4d4d1..74cc43f6 100644
--- a/include/xo/tokenizer/tokenizer.hpp
+++ b/include/xo/tokenizer/tokenizer.hpp
@@ -31,12 +31,16 @@ namespace xo {
          *    span_type input = ...;
          *
          *    while (!input.empty()) {
-         *        auto res = tkz.scan(input);
-         *        auto [tk, consumed, error] = res.first;
+         *        auto [tk, consumed, error] = tkz.scan(input);
          *
-         *        // do something with tk if tk.is_valid()
+         *        if (tk.is_valid()) {
+         *            // do something with tk
+         *        } else if (error.is_error()) {
+         *            error.report(cout);
+         *            break;
+         *        }
          *
-         *        input = tkz.consume(res.second, input);
+         *        input = tkz.consume(consumed, input);
          *    }
          *
          *    if endofinput {
diff --git a/include/xo/tokenizer/tokenizer_error.hpp b/include/xo/tokenizer/tokenizer_error.hpp
index 9488b62b..743e3faf 100644
--- a/include/xo/tokenizer/tokenizer_error.hpp
+++ b/include/xo/tokenizer/tokenizer_error.hpp
@@ -27,7 +27,7 @@ namespace xo {
             /** @defgroup tokenizer-error-ctors **/
             ///@{
 
-            /** Default ctor represent a not-an-error sentinel object **/
+            /** Default ctor represents a not-an-error sentinel object **/
             tokenizer_error() = default;
             /** Constructor to capture parsing error context
              *  @p tk_start   current position on entry to scanner
@@ -69,7 +69,7 @@ namespace xo {
 
             /** true, except for a sentinel error object **/
             bool is_error() const { return error_description_ != nullptr; }
-            /** true except for object in sentinel state **/
+            /** false except for object in sentinel state **/
             bool is_not_an_error() const { return error_description_ == nullptr; }
 
             /** Print representation to stream @p os. Intended for tokenizer diagnostics.