feat: Improve index of compile time (#165)

benchmark/components/index_of_benchmark.cpp

@@ -1,10 +1,111 @@
-#include <iostream>
-
-#include "ComplexStateMachine.h"
 #include "hsm/details/index_map.h"
 
 using namespace hsm;
 
+namespace {
+class s1 {
+};
+class s2 {
+};
+class s3 {
+};
+class s4 {
+};
+class s5 {
+};
+class s6 {
+};
+class s7 {
+};
+class s8 {
+};
+class s9 {
+};
+class s10 {
+};
+class s11 {
+};
+class s12 {
+};
+class s13 {
+};
+class s14 {
+};
+class s15 {
+};
+class s16 {
+};
+class s17 {
+};
+class s18 {
+};
+class s19 {
+};
+class s20 {
+};
+class s21 {
+};
+class s22 {
+};
+class s23 {
+};
+class s24 {
+};
+class s25 {
+};
+class s26 {
+};
+class s27 {
+};
+class s28 {
+};
+class s29 {
+};
+class s30 {
+};
+class s31 {
+};
+class s32 {
+};
+class s33 {
+};
+class s34 {
+};
+class s35 {
+};
+class s36 {
+};
+class s37 {
+};
+class s38 {
+};
+class s39 {
+};
+class s40 {
+};
+class s41 {
+};
+class s42 {
+};
+class s43 {
+};
+class s44 {
+};
+class s45 {
+};
+class s46 {
+};
+class s47 {
+};
+class s48 {
+};
+class s49 {
+};
+class s50 {
+};
+
+}
+
 int main()
 {
  using namespace boost::hana;

include/hsm/details/fill_dispatch_table.h

@@ -75,6 +75,8 @@ constexpr auto addDispatchTableEntry(
  [=](auto& dispatchTable, auto&& transition2, bool internal) -> void {
  const auto defer = false;
  const auto valid = true;
+
+ // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
  dispatchTable[fromIdx].push_front(
  { toIdx, history, defer, valid, internal, std::move(transition2) });
  },

include/hsm/details/index_map.h

@@ -11,21 +11,41 @@
 #include <boost/hana/basic_tuple.hpp>
 #include <boost/hana/zip.hpp>
 
-//#include <boost/mp11.hpp>
+namespace {
+template <class X, class Tuple> class GetIdx;
+
+template <class X, class... T> class GetIdx<X, boost::hana::tuple<T...>> {
+ template <std::size_t... idx>
+ static constexpr auto find_idx(std::index_sequence<idx...> seq) -> std::size_t
+ {
+ return seq.size() + ((std::is_same<X, T>::value ? idx - seq.size() : 0) + ...);
+ }
+
+ public:
+ static constexpr std::size_t value = find_idx(std::index_sequence_for<T...> {});
+};
+
+template <class X, class... T> class GetIdx<X, boost::hana::basic_tuple<T...>> {
+ template <std::size_t... idx>
+ static constexpr auto find_idx(std::index_sequence<idx...> seq) -> std::size_t
+ {
+ return seq.size() + ((std::is_same<X, T>::value ? idx - seq.size() : 0) + ...);
+ }
+
+ public:
+ static constexpr std::size_t value = find_idx(std::index_sequence_for<T...> {});
+};
+}
 
 namespace hsm {
 
 namespace bh {
 using namespace boost::hana;
 }
 
-template <class Iterable, class Element>
-constexpr auto index_of(Iterable const& iterable, Element const& element)
+template <class Iterable, class Element> constexpr auto index_of(Iterable const&, Element const&)
 {
- return bh::apply(
- [](auto size, auto dropped) { return size - dropped; },
- bh::size(iterable),
- bh::size(bh::drop_while(iterable, bh::not_equal.to(element))));
+ return GetIdx<Element, Iterable>::value;
 }
 
 template <class Typeids> constexpr auto make_index_map(Typeids typeids)

test/unit/stateidx_tests.cpp

@@ -1,6 +1,8 @@
 #include "hsm/details/fill_dispatch_table.h"
+#include "hsm/details/index_map.h"
 #include "hsm/details/state.h"
 #include "hsm/details/transition_table.h"
+
 #include "hsm/front/transition_tuple.h"
 
 #include <gtest/gtest.h>