xo-interpreter2: refactor to setup vsm utest + repl

include/xo/interpreter2/VirtualSchematikaMachine.hpp

@@ -14,6 +14,23 @@
 
 namespace xo {
     namespace scm {
+        /** similar to @ref xo::scm::ReaderResult **/
+        struct VsmResult {
+            using AGCObject = xo::mm::AGCObject;
+            using span_type = xo::mm::span<const char>;
+
+            bool is_tk_error() const { return tk_error_.is_error(); }
+
+            /** result of evaluating first expression encountered in input **/
+            obj<AGCObject> value_;
+
+            /** unconsumed portion of input span **/
+            span_type remaining_input_;
+
+            /** {src_function, error_description, input_state, error_pos} **/
+            TokenizerError tk_error_;
+        };
+
         /** @class VirtualSchematikaMachine
          *  @brief virtual machine for schematika
          **/
@@ -23,10 +40,17 @@ namespace xo {
             using Stack = void *;
             using AAllocator = xo::mm::AAllocator;
             using AGCObject = xo::mm::AGCObject;
+            using span_type = xo::mm::span<const char>;
 
         public:
             VirtualSchematikaMachine(const VsmConfig & config);
 
+            /** consume input @p input_cstr **/
+            VsmResult read_eval_print(span_type input_span, bool eof);
+
+            /** evaluate expression @p expr **/
+            std::pair<obj<AGCObject>, TokenizerError> eval(obj<AExpression> expr);
+
             /** borrow calling thread to run indefinitely,
              *  until halt instruction
              **/

include/xo/interpreter2/VsmConfig.hpp

@@ -10,11 +10,13 @@
 
 namespace xo {
     namespace scm {
-        /** Configuration for virtual schematika machine 
+        /** Configuration for virtual schematika machine
          **/
         struct VsmConfig {
             using X1CollectorConfig = xo::mm::X1CollectorConfig;
 
+            VsmConfig() = default;
+
             /** reader configuration **/
             ReaderConfig rdr_config_;
             /** Configuration for allocator/collector.

src/interpreter2/VirtualSchematikaMachine.cpp

@@ -8,10 +8,18 @@
 #include <xo/expression2/DConstant.hpp>
 #include <xo/gc/DX1Collector.hpp>
 #include <xo/gc/detail/IAllocator_DX1Collector.hpp>
+#include <xo/printable2/Printable.hpp>
+#include <xo/facet/FacetRegistry.hpp>
 #include <cassert>
 
 namespace xo {
+    using xo::print::APrintable;
+    using xo::print::ppconfig;
+    using xo::print::ppstate_standalone;
+    using xo::mm::AGCObject;
     using xo::mm::DX1Collector;
+    using xo::facet::FacetRegistry;
+    using std::cout;
 
     namespace scm {
 
@@ -21,6 +29,52 @@ namespace xo {
           reader_{config.rdr_config_, mm_.to_op()}
         {}
 
+        VsmResult
+        VirtualSchematikaMachine::read_eval_print(span_type input, bool eof)
+        {
+            if (input.empty()) {
+                return VsmResult();
+            }
+
+            auto [expr, remaining, error1]
+                = reader_.read_expr(input, eof);
+
+            if (!expr) {
+                return {
+                    .remaining_input_ = remaining,
+                    .tk_error_ = error1
+                };
+            }
+
+            auto [value, error2] = this->eval(expr);
+
+            if (!value) {
+                return {
+                    .remaining_input_ = remaining,
+                    .tk_error_ = error2
+                };
+            }
+
+            obj<APrintable> value_pr
+                = FacetRegistry::instance().variant<APrintable,AGCObject>(value);
+
+            // pretty_toplevel(value_pr, &cout, ppconfig());
+            ppconfig ppc;
+            ppstate_standalone pps(&cout, 0, &ppc);
+            pps.prettyn(value_pr);
+
+            return { .remaining_input_ = remaining };
+        }
+
+        std::pair<obj<AGCObject>, TokenizerError>
+        VirtualSchematikaMachine::eval(obj<AExpression> expr)
+        {
+            (void)expr;
+
+            assert(false);
+            return std::make_pair(obj<AGCObject>(), TokenizerError());
+        }
+
         void
         VirtualSchematikaMachine::run()
         {

utest/VirtualSchematikaMachine.test.cpp

@@ -20,6 +20,9 @@
 #include <catch2/catch.hpp>
 
 namespace xo {
+    using xo::scm::VirtualSchematikaMachine;
+    using xo::scm::VsmConfig;
+
 #ifdef NOT_YET
     using xo::scm::SchematikaParser;
     using xo::scm::ASyntaxStateMachine;
@@ -42,6 +45,8 @@ namespace xo {
     namespace ut {
         TEST_CASE("VirtualSchematikaMachine-ctor", "[interpreter2][VSM]")
         {
+            VirtualSchematikaMachine vsm(VsmConfig);
+
 #ifdef NOT_YET
             ArenaConfig config;
             config.name_ = "test-arena";