xo-reader: tidy: + begin/end translation unit methods

include/xo/parser/reader.hpp

@@ -31,6 +31,7 @@ namespace xo {
          *  Use:
          *  @code
          *    reader rdr;
+         *    rdr.begin_translation_unit()
          *
          *    bool eof = false;
          *    while (!eof) {
@@ -63,6 +64,22 @@ namespace xo {
         public:
             reader() = default;
 
+            /** call once before calling .read_expr():
+             *  1. with new reader
+             *  2. if last read_expr() call had eof=true
+             **/
+            void begin_translation_unit();
+
+            /** counterpart to .begin_translation_unit(),
+             *  provided for symmetry's sake
+             *
+             *  Equivalent to:
+             *  @code
+             *    read_expr(span_type(nullptr, nullptr), true);
+             *  @endcode
+             **/
+            reader_result end_translation_unit();
+
             /** Try to read one expression from @p input.
              *  Return struct containing parsed expression
              *  and span of characters comprising that expression

src/parser/reader.cpp

@@ -4,6 +4,16 @@
 
 namespace xo {
     namespace scm {
+        void
+        reader::begin_translation_unit() {
+            parser_.begin_translation_unit();
+        }
+
+        reader_result
+        reader::end_translation_unit() {
+            return this->read_expr(span_type(nullptr, nullptr), true /*eof*/);
+        }
+
         reader_result
         reader::read_expr(const span_type & input_arg, bool eof)
         {