add Chapter18

Chapter18/cib/libs/flow/detail/par.hpp

@@ -0,0 +1,72 @@
+#pragma once
+
+#include <flow/detail/walk.hpp>
+#include <flow/subgraph_identity.hpp>
+
+#include <stdx/tuple_algorithms.hpp>
+
+namespace flow::dsl {
+template <subgraph Lhs, subgraph Rhs,
+          subgraph_identity Identity = subgraph_identity::REFERENCE>
+struct par {
+    Lhs lhs;
+    Rhs rhs;
+
+    using is_subgraph = void;
+
+    constexpr auto operator*() const {
+        return par<Lhs, Rhs, subgraph_identity::VALUE>{Lhs{}, Rhs{}};
+    }
+
+  private:
+    friend constexpr auto tag_invoke(get_initials_t, par const &p) {
+        return stdx::tuple_cat(get_initials(p.lhs), get_initials(p.rhs));
+    }
+
+    friend constexpr auto tag_invoke(get_finals_t, par const &p) {
+        return stdx::tuple_cat(get_finals(p.lhs), get_finals(p.rhs));
+    }
+
+    friend constexpr auto tag_invoke(get_nodes_t, par const &p) {
+        if constexpr (Identity == subgraph_identity::VALUE) {
+            auto all_nodes = stdx::to_unsorted_set(
+                stdx::tuple_cat(get_all_mentioned_nodes(p.lhs),
+                                get_all_mentioned_nodes(p.rhs)));
+
+            return stdx::transform([](auto const &n) { return *n; }, all_nodes);
+
+        } else {
+            return stdx::tuple_cat(get_nodes(p.lhs), get_nodes(p.rhs));
+        }
+    }
+
+    friend constexpr auto tag_invoke(get_all_mentioned_nodes_t, par const &p) {
+        return stdx::tuple_cat(get_all_mentioned_nodes(p.lhs),
+                               get_all_mentioned_nodes(p.rhs));
+    }
+
+    friend constexpr auto tag_invoke(get_edges_t, par const &p) {
+        return stdx::tuple_cat(get_edges(p.lhs), get_edges(p.rhs));
+    }
+};
+
+template <subgraph Lhs, subgraph Rhs> par(Lhs, Rhs) -> par<Lhs, Rhs>;
+} // namespace flow::dsl
+
+template <flow::dsl::subgraph Lhs, flow::dsl::subgraph Rhs>
+[[nodiscard]] constexpr auto operator&&(Lhs const &lhs, Rhs const &rhs) {
+    return flow::dsl::par{lhs, rhs};
+}
+
+template <typename Cond, flow::dsl::subgraph Lhs, flow::dsl::subgraph Rhs,
+          flow::subgraph_identity Identity>
+constexpr auto make_runtime_conditional(Cond,
+                                        flow::dsl::par<Lhs, Rhs, Identity>) {
+    auto lhs = make_runtime_conditional(Cond{}, Lhs{});
+    auto rhs = make_runtime_conditional(Cond{}, Rhs{});
+
+    using lhs_t = decltype(lhs);
+    using rhs_t = decltype(rhs);
+
+    return flow::dsl::par<lhs_t, rhs_t, Identity>{lhs, rhs};
+}