From b5608dc9d4739dbb97798d83fd7821a051c6afe2 Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Sat, 25 Jun 2022 23:20:28 -0700
Subject: Use a separate EvalContext structure for holding some state.

---
 aisa/eval.h | 16 +++++++++++++++-
 main.cpp    | 17 +++++++++--------
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/aisa/eval.h b/aisa/eval.h
index 30dc617..a301e93 100644
--- a/aisa/eval.h
+++ b/aisa/eval.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <coroutine>
+#include <memory>
 #include <optional>
 #include <utility>
 #include <vector>
@@ -11,6 +12,12 @@
 namespace aisa {
 
     template<typename CRTP> struct EvalState {
+        struct EvalContext {
+            task<void> coroutine;
+
+            bool resume() { return coroutine(); }
+        };
+
         CRTP & crtp() noexcept { return static_cast<CRTP &>(*this); }
 
         task<regval_t> async_load_reg(regnum_t rn)
@@ -31,7 +38,7 @@ namespace aisa {
             }
         }
 
-        task<void> eval(const Step &step)
+        task<void> async_evaluate(EvalContext &contex, const Step &step)
         {
             if (step.predicate.has_value()) {
                 regval_t pval = co_await async_load_reg(step.predicate->first);
@@ -46,6 +53,13 @@ namespace aisa {
             for (unsigned int i = 0; i < step.destination_regs.size(); ++i)
                 co_await async_store_reg(step.destination_regs[i], destination_vals[i]);
         }
+
+        std::unique_ptr<EvalContext> operator()(const Step &step)
+        {
+            auto context = std::make_unique<EvalContext>();
+            context->coroutine = async_evaluate(*context, step);
+            return context;
+        }
     };
 
 }
diff --git a/main.cpp b/main.cpp
index df2aca1..e88d740 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1,6 +1,7 @@
 #include <initializer_list>
 #include <iostream>
 #include <map>
+#include <memory>
 #include <optional>
 #include <string>
 #include <type_traits>
@@ -69,18 +70,18 @@ int main(int argc, const char *argv[])
 
     std::cout << "\n\n\n";
 
-    auto w = state.eval(step);
-    std::cout << "run\n"; w();
-    std::cout << "run\n"; w();
-    std::cout << "run\n"; w();
+    auto w = state(step);
+    std::cout << "run\n"; w->resume();
+    std::cout << "run\n"; w->resume();
+    std::cout << "run\n"; w->resume();
     std::cout << "set predicate (valid)\n"; state.store_reg(step.predicate->first, step.predicate->second);
-    std::cout << "run\n"; w();
-    std::cout << "run\n"; w();
-    std::cout << "run\n"; w();
+    std::cout << "run\n"; w->resume();
+    std::cout << "run\n"; w->resume();
+    std::cout << "run\n"; w->resume();
     std::cout << "set regs (all)\n";
     for (int i = 0; i < 10; ++i)
         state.store_reg(i, 1000 + i);
-    for (bool done = false; !done; done = w())
+    for (bool done = false; !done; done = w->resume())
         std::cout << "run\n";
     std::cout << "huzzah!\n";
 
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