From a68815b3cdabfefc27bf8a962fbc00b2f501d81d Mon Sep 17 00:00:00 2001
From: King_DuckZ <king_duckz@gmx.com>
Date: Mon, 7 Jun 2021 20:01:34 +0200
Subject: [PATCH] Same conversion but without any lookup

---
 include/duckhandy/implem/int_conv.hpp | 12 ++----------
 speed_test_int_conv.cpp               |  2 +-
 2 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/include/duckhandy/implem/int_conv.hpp b/include/duckhandy/implem/int_conv.hpp
index ded9174..2fd9239 100644
--- a/include/duckhandy/implem/int_conv.hpp
+++ b/include/duckhandy/implem/int_conv.hpp
@@ -159,14 +159,6 @@ namespace dhandy {
 				using RetType = RevArray<I, 10, Tr>;
 				using Num = implem::NumberAdaptation<I, 10>;
 
-				//How to build this lookup: 1) write numbers 0, 10, 20..., 90
-				//in binary; 2) take the lowest 5 bits, div by 2 and write as
-				//decimal; 3) divide by 2; 4) the result is the position in the
-				//below array that should be filled in with the leading digit
-				//from the original 0-90 number
-				constexpr const char lookup[16] = {
-					 0, 0, 0, 7, 4, 1, 0, 0, 8, 5, 2, 0, 0, 9, 6, 3
-				};
 				const bool was_negative = implem::is_negative<I, 10>(in);
 
 				RetType arr;
@@ -178,7 +170,7 @@ namespace dhandy {
 					const auto last_two = in % 100;
 					const auto digit_low = in % 10;
 					in = static_cast<I>(in / static_cast<I>(100));
-					const auto digit_high = lookup[((last_two - digit_low) >> 1) & 0xF];
+					const auto digit_high = last_two / 10;
 					arr.push_front(Tr::to_digit(static_cast<int>(digit_low)));
 					arr.push_front(Tr::to_digit(static_cast<int>(digit_high)));
 				};
@@ -187,7 +179,7 @@ namespace dhandy {
 				}
 				else {
 					const auto digit_low = in % 10;
-					const auto digit_high = lookup[((in - digit_low) >> 1) & 0xF];
+					const auto digit_high = (in / 10) % 10;
 					arr.push_front(Tr::to_digit(static_cast<int>(digit_low)));
 					arr.push_front(Tr::to_digit(static_cast<int>(digit_high)));
 				}
diff --git a/speed_test_int_conv.cpp b/speed_test_int_conv.cpp
index d62c945..063ce95 100644
--- a/speed_test_int_conv.cpp
+++ b/speed_test_int_conv.cpp
@@ -33,7 +33,7 @@ void run_with_timing (
 
 int main() {
 	using dhandy::int_conv;
-	constexpr const std::size_t count = 50'000'000;
+	constexpr const std::size_t count = 70'000'000;
 
 	std::vector<unsigned int> nums;
 	std::vector<std::string> strings;