xo-reader2: working on example parser repl

include/xo/reader2/SchematikaReader.hpp

@@ -0,0 +1,70 @@
+/** @file SchematikaReader.hpp
+*
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include "ReaderConfig.hpp"
+#include "SchematikaParser.hpp"
+#include <xo/tokenizer2/Tokenizer.hpp>
+
+namespace xo {
+    namespace scm {
+        struct ReaderResult {
+            using span_type = xo::mm::span<const char>;
+
+            bool is_tk_error() const { return tk_error_.is_error(); }
+
+            /** schematika expression parsed from input **/
+            obj<AExpression> expr_;
+            /** input span up to end of expression.
+             *  only relevant when result type is expression.
+             *  (otherwise treat entire input as consumed)
+             **/
+            span_type consumed_;
+
+            /** {src_function, error_description, input_state, error_pos} **/
+            TokenizerError tk_error_;
+        };
+
+        /** @class SchematikaReader
+         *  @brief Pipeline comprising Schematika tokenizer and parser
+         *
+         *  Consumes text; produces expressions
+         **/
+        class SchematikaReader {
+        public:
+            using AAllocator = xo::mm::AAllocator;
+
+        public:
+            SchematikaReader(const ReaderConfig & config,
+                             obj<AAllocator> expr_alloc);
+
+            /** prepare interactive session
+             *  (allows rvalue expressions at toplevel)
+             **/
+            void begin_interactive_session();
+
+            /** consume input @p input_cstr **/
+            const ReaderResult & read_expr(const char * input_cstr, bool eof);
+
+        private:
+            /** tokenizer converts a stream of chars
+             *  to a stream of lexical tokens
+             **/
+            Tokenizer tokenizer_;
+
+            /** parser converts a stream of tokens
+             *  to a stream of expressions
+             **/
+            SchematikaParser parser_;
+
+            /** current output from reader **/
+            ReaderResult result_;
+
+        };
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end SchematikaReader.hpp */