From 15e1e506595920c3f7ce74cb92fdbdff040e5f5c Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Thu, 22 Jan 2026 17:41:40 -0500
Subject: [PATCH] xo-reader2: accept parsed expression at top level..

---
 include/xo/reader2/ParserResult.hpp       |  6 ++++++
 include/xo/reader2/ParserStateMachine.hpp |  4 ++++
 src/reader2/DExprSeqState.cpp             | 12 +++++-------
 src/reader2/ParserResult.cpp              | 10 ++++++++++
 src/reader2/ParserStateMachine.cpp        |  9 ++++++++-
 5 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/include/xo/reader2/ParserResult.hpp b/include/xo/reader2/ParserResult.hpp
index 45064d32..6592c7da 100644
--- a/include/xo/reader2/ParserResult.hpp
+++ b/include/xo/reader2/ParserResult.hpp
@@ -41,6 +41,12 @@ namespace xo {
                          std::string_view error_src_fn,
                          const DString * error_description);
 
+            /** create ParserResult for parsing success;
+             *  parsing yields expression @p expr
+             **/
+            static ParserResult expression(std::string_view ssm,
+                                           obj<AExpression> expr);
+
             /** create ParserResult for a parsing error.
              *  Reporting detailed message @p errmsg
              *  from syntax state machine @p ssm
diff --git a/include/xo/reader2/ParserStateMachine.hpp b/include/xo/reader2/ParserStateMachine.hpp
index 42c8af64..b838efe5 100644
--- a/include/xo/reader2/ParserStateMachine.hpp
+++ b/include/xo/reader2/ParserStateMachine.hpp
@@ -148,6 +148,10 @@ namespace xo {
             /** @defgroup scm-parserstatemachine-error-entrypoints error entry points **/
             ///@{
 
+            /** capture result expression @p expr **/
+            void capture_result(std::string_view ssm_anme,
+                                obj<AExpression> expr);
+
             /** capture error message @p errmsg from @p ssm_name,
              *  as current state machine output.
              *
diff --git a/src/reader2/DExprSeqState.cpp b/src/reader2/DExprSeqState.cpp
index e67790d5..33a68c15 100644
--- a/src/reader2/DExprSeqState.cpp
+++ b/src/reader2/DExprSeqState.cpp
@@ -218,18 +218,16 @@ namespace xo {
         DExprSeqState::on_parsed_expression(obj<AExpression> expr,
                                             ParserStateMachine * p_psm)
         {
-            p_psm->illegal_parsed_expression("DExprSeqState::on_parsed_expression",
-                                             expr,
-                                             this->get_expect_str());
+            // toplevel expr sequence accepts an arbitrary number of expressions.
+
+            p_psm->capture_result("DExprSeqState::on_parsed_expression", expr);
         }
 
         void
         DExprSeqState::on_parsed_expression_with_semicolon(obj<AExpression> expr,
-                                                          ParserStateMachine * p_psm)
+                                                           ParserStateMachine * p_psm)
         {
-            p_psm->illegal_parsed_expression("DExprSeqState::on_parsed_expression_with_semicolon",
-                                             expr,
-                                             this->get_expect_str());
+            p_psm->capture_result("DExprSeqState::on_parsed_expression_with_semicolon", expr);
         }
 
         bool
diff --git a/src/reader2/ParserResult.cpp b/src/reader2/ParserResult.cpp
index 312538b1..974724d9 100644
--- a/src/reader2/ParserResult.cpp
+++ b/src/reader2/ParserResult.cpp
@@ -36,6 +36,16 @@ namespace xo {
                   error_description_{error_description}
         {}
 
+        ParserResult
+        ParserResult::expression(std::string_view ssm_name,
+                                 obj<AExpression> expr)
+        {
+            return ParserResult(parser_result_type::expression,
+                                expr,
+                                ssm_name,
+                                nullptr);
+        }
+
         ParserResult
         ParserResult::error(std::string_view ssm_name,
                             const DString * errmsg)
diff --git a/src/reader2/ParserStateMachine.cpp b/src/reader2/ParserStateMachine.cpp
index 66e4703e..80841fd8 100644
--- a/src/reader2/ParserStateMachine.cpp
+++ b/src/reader2/ParserStateMachine.cpp
@@ -288,6 +288,13 @@ namespace xo {
             stack_->top().on_semicolon_token(tk, this);
         }
 
+        void
+        ParserStateMachine::capture_result(std::string_view ssm_name,
+                                           obj<AExpression> expr)
+        {
+            this->result_ = ParserResult::expression(ssm_name, expr);
+        }
+
         void
         ParserStateMachine::capture_error(std::string_view ssm_name,
                                           const DString * errmsg)
@@ -321,7 +328,7 @@ namespace xo {
         void
         ParserStateMachine::illegal_input_on_symbol(std::string_view ssm_name,
                                                     std::string_view sym,
-                                                   std::string_view expect_str)
+                                                    std::string_view expect_str)
         {
             // TODO:
             // - want to write error message using DArena