xo-reader2: skeleton DExpectExprSsm.*

xo-reader2/include/xo/reader2/DExpectExprSsm.hpp

@@ -0,0 +1,113 @@
+/** @file DExpectExprSsm.hpp
+*
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include "ParserStateMachine.hpp"
+#include "syntaxstatetype.hpp"
+//#include <xo/arena/DArena.hpp>
+#include <xo/facet/obj.hpp>
+#include <xo/indentlog/print/ppindentinfo.hpp>
+
+namespace xo {
+    namespace scm {
+
+        class DExpectExprSsm {
+        public:
+            using TypeDescr = xo::reflect::TypeDescr;
+            using DArena = xo::mm::DArena;
+            using ppindentinfo = xo::print::ppindentinfo;
+
+        public:
+            explicit DExpectExprSsm(bool allow_defs,
+                                    bool cxl_on_rightparen);
+
+            static DExpectExprSsm * make(DArena & parser_mm,
+                                         bool allow_defs,
+                                         bool cxl_on_rightparen);
+
+            static void start(DArena & parser_mm,
+                              bool allow_defs,
+                              bool cxl_on_rightparen,
+                              ParserStateMachine * p_psm);
+
+            /** @defgroup scm-expectexpr-ssm-facet syntaxstatemachine facet methods **/
+            ///@{
+
+            /** identifies the ssm implemented here **/
+            syntaxstatetype ssm_type() const noexcept;
+
+            /** text describing expected/allowed input to this ssm in current state.
+             *  Intended to drive error mesages
+             **/
+            std::string_view get_expect_str() const noexcept;
+
+            /** operate state machine for this syntax on incoming symbol-token @p tk
+             *  with overall parser state in @p p_psm
+             **/
+            void on_symbol_token(const Token & tk,
+                                 ParserStateMachine * p_psm);
+
+            /** update state for this syntax on incoming token @p tk,
+             *  overall parser state in @p p_psm
+             **/
+            void on_def_token(const Token & tk,
+                              ParserStateMachine * p_psm);
+
+            /** update state for this syntax on incoming token @p tk,
+             *  overall parser state in @p p_psm
+             **/
+            void on_if_token(const Token & tk,
+                             ParserStateMachine * p_psm);
+
+            /** update state for this syntax on incoming colon token @p tk,
+             *  overall parser state in @p p_psm
+             **/
+            void on_colon_token(const Token & tk,
+                                ParserStateMachine * p_psm);
+
+            /** update state for this syntax on incoming singleassign token @p tk,
+             *  overall parser state in @p p_psm
+             **/
+            void on_singleassign_token(const Token & tk,
+                                       ParserStateMachine * p_psm);
+
+            /** update state for this syntax after parsing a symbol @p sym;
+             *  overall parser state in @p p_psm
+             **/
+            void on_parsed_symbol(std::string_view sym,
+                                  ParserStateMachine * p_psm);
+
+            /** update state for this syntax after parsing a type-description @p td,
+             *  overall parser state in @p p_psm
+             **/
+            void on_parsed_typedescr(TypeDescr td,
+                                     ParserStateMachine * p_psm);
+
+            ///@}
+            /** @defgroup scm-define-printable-facet printable facet methods **/
+            ///@{
+
+            bool pretty(const ppindentinfo & ppii) const;
+
+            ///@}
+
+        private:
+            /** if true: allow a define-expression here; otherwise reject **/
+            bool allow_defs_ = false;
+            /** if true: expecting either:
+             *  1a. expression
+             *  1b. right brace '}', in which case no expression
+             *  if false: expecting only:
+             *  2a. expression
+             **/
+            bool cxl_on_rightbrace_ = false;
+
+
+        };
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DExpectExprSsm.hpp */