From 3e29bf78c79155f39d4d27d570e700998c89a0b6 Mon Sep 17 00:00:00 2001
From: Daniel Lemire <daniel@lemire.me>
Date: Thu, 3 Nov 2022 19:40:05 -0400
Subject: [PATCH] Nicer constants.

---
 include/fast_float/float_common.h | 61 ++++++++++++++-----------------
 1 file changed, 28 insertions(+), 33 deletions(-)

diff --git a/include/fast_float/float_common.h b/include/fast_float/float_common.h
index 7f14914..f051667 100644
--- a/include/fast_float/float_common.h
+++ b/include/fast_float/float_common.h
@@ -220,7 +220,8 @@ constexpr static double powers_of_ten_double[] = {
     1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22};
 constexpr static float powers_of_ten_float[] = {1e0, 1e1, 1e2, 1e3, 1e4, 1e5,
                                                 1e6, 1e7, 1e8, 1e9, 1e10};
-
+// used for max_mantissa_double and max_mantissa_float
+constexpr uint64_t constant_55555 = 5 * 5 * 5 * 5 * 5;
 // Largest integer value v so that (5**index * v) <= 1<<53.
 // 0x10000000000000 == 1 << 53
 constexpr static uint64_t max_mantissa_double[] = {
@@ -229,31 +230,25 @@ constexpr static uint64_t max_mantissa_double[] = {
       0x10000000000000 / (5 * 5),
       0x10000000000000 / (5 * 5 * 5),
       0x10000000000000 / (5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 *
-           5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 *
-           5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 *
-           5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 *
-           5 * 5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 *
-           5 * 5 * 5 * 5 * 5),
-      0x10000000000000 / (uint64_t(5) * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 *
-           5 * 5 * 5 * 5 * 5 * 5)};
+      0x10000000000000 / (constant_55555),
+      0x10000000000000 / (constant_55555 * 5),
+      0x10000000000000 / (constant_55555 * 5 * 5),
+      0x10000000000000 / (constant_55555 * 5 * 5 * 5),
+      0x10000000000000 / (constant_55555 * 5 * 5 * 5 * 5),
+      0x10000000000000 / (constant_55555 * constant_55555),
+      0x10000000000000 / (constant_55555 * constant_55555 * 5),
+      0x10000000000000 / (constant_55555 * constant_55555 * 5 * 5),
+      0x10000000000000 / (constant_55555 * constant_55555 * 5 * 5 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * 5 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * 5 * 5 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * 5 * 5 * 5 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * constant_55555),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * constant_55555 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * constant_55555 * 5 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * constant_55555 * 5 * 5 * 5),
+      0x10000000000000 / (constant_5555constant_55555 * constant_55555 * constant_55555 * 5 * 5 * 5 * 5)};
   // Largest integer value v so that (5**index * v) <= 1<<24.
   // 0x1000000 == 1<<24
   constexpr static uint64_t max_mantissa_float[] = {
@@ -262,13 +257,13 @@ constexpr static uint64_t max_mantissa_double[] = {
       0x1000000 / (5 * 5),
       0x1000000 / (5 * 5 * 5),
       0x1000000 / (5 * 5 * 5 * 5),
-      0x1000000 / (5 * 5 * 5 * 5 * 5),
-      0x1000000 / (5 * 5 * 5 * 5 * 5 * 5),
-      0x1000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x1000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x1000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x1000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5),
-      0x1000000 / (5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5)};
+      0x1000000 / (constant_55555),
+      0x1000000 / (constant_55555 * 5),
+      0x1000000 / (constant_55555 * 5 * 5),
+      0x1000000 / (constant_55555 * 5 * 5 * 5),
+      0x1000000 / (constant_55555 * 5 * 5 * 5 * 5),
+      0x1000000 / (constant_55555 * constant_55555),
+      0x1000000 / (constant_55555 * constant_55555 * 5)};
 
 template <typename T> struct binary_format {
   using equiv_uint = typename std::conditional<sizeof(T) == 4, uint32_t, uint64_t>::type;