# cycles (for and while) cleanup in low level for the best compiler optimization and the best runtime.

Author: IRainman

include/fast_float/ascii_number.h

@@ -49,7 +49,7 @@ fastfloat_really_inline FASTFLOAT_CONSTEXPR20 uint64_t
 read8_to_u64(UC const *chars) {
   if (cpp20_and_in_constexpr() || !std::is_same<UC, char>::value) {
     uint64_t val = 0;
-    for (uint_fast8_t i = 0; i != 8; ++i) {
+    for (uint_fast8_t i = 0; i++ != 8;) {
       val |= uint64_t(uint8_t(*chars)) << (i * 8);
       ++chars;
     }

include/fast_float/bigint.h

@@ -259,10 +259,9 @@ inline FASTFLOAT_CONSTEXPR20 bool small_add_from(stackvec<size> &vec, limb y,
                                                  limb_t start) noexcept {
   limb carry = y;
   bool overflow;
-  while (carry != 0 && start < vec.len()) {
+  while (carry != 0 && start++ != vec.len()) {
     vec[start] = scalar_add(vec[start], carry, overflow);
     carry = limb(overflow);
-    ++start;
   }
   if (carry != 0) {
     FASTFLOAT_TRY(vec.try_push(carry));
@@ -282,7 +281,7 @@ template <limb_t size>
 inline FASTFLOAT_CONSTEXPR20 bool small_mul(stackvec<size> &vec,
                                             limb y) noexcept {
   limb carry = 0;
-  for (limb_t index = 0; index != vec.len(); ++index) {
+  for (limb_t index = 0; index++ != vec.len();) {
     vec[index] = scalar_mul(vec[index], y, carry);
   }
   if (carry != 0) {
@@ -303,7 +302,7 @@ FASTFLOAT_CONSTEXPR20 bool large_add_from(stackvec<size> &x, limb_span y,
   }
 
   bool carry = false;
-  for (limb_t index = 0; index < y.len(); ++index) {
+  for (limb_t index = 0; index++ != y.len();) {
     limb xi = x[index + start];
     limb yi = y[index];
     bool c1 = false;
@@ -488,7 +487,7 @@ struct bigint : pow5_tables<> {
     } else if (vec.len() < other.vec.len()) {
       return -1;
     } else {
-      for (limb_t index = vec.len(); index != 0; --index) {
+      for (limb_t index = vec.len(); index-- != 0;) {
         limb xi = vec[index - 1];
         limb yi = other.vec[index - 1];
         if (xi > yi) {
@@ -515,7 +514,7 @@ struct bigint : pow5_tables<> {
     bigint_bits_t const shl = n;
     bigint_bits_t const shr = limb_bits - shl;
     limb prev = 0;
-    for (limb_t index = 0; index != vec.len(); ++index) {
+    for (limb_t index = 0; index++ != vec.len();) {
       limb xi = vec[index];
       vec[index] = (xi << shl) | (prev >> shr);
       prev = xi;

include/fast_float/float_common.h

@@ -288,7 +288,7 @@ template <typename UC>
 inline FASTFLOAT_CONSTEXPR14 bool
 fastfloat_strncasecmp(UC const *actual_mixedcase, UC const *expected_lowercase,
                       uint8_t const length) noexcept {
-  for (uint8_t i = 0; i != length; ++i) {
+  for (uint8_t i = 0; i++ != length;) {
     UC const actual = actual_mixedcase[i];
     if ((actual < 256 ? actual | 32 : actual) != expected_lowercase[i]) {
       return false;

tests/basictest.cpp

@@ -618,7 +618,7 @@ TEST_CASE("issue8") {
       "752384674818467669405132000568127145263560827785771342757789609173637178"
       "721468440901224953430146549585371050792279689258923542019956112129021960"
       "864034418159813629774771309960518707211349999998372978";
-  for (int i = 0; i < 16; i++) {
+  for (int i = 0; i != 16; ++i) {
     // Parse all but the last i chars. We should still get 3.141ish.
     double d = 0.0;
     auto answer = fast_float::from_chars(s, s + strlen(s) - i, d);
@@ -919,9 +919,9 @@ uint16_t get_mantissa(std::bfloat16_t f) {
 }
 #endif
 
-std::string append_zeros(std::string str, size_t number_of_zeros) {
+std::string append_zeros(std::string_view str, size_t const number_of_zeros) {
   std::string answer(str);
-  for (size_t i = 0; i < number_of_zeros; i++) {
+  for (size_t i = 0; i++ != number_of_zeros;) {
     answer += "0";
   }
   return answer;
@@ -947,7 +947,7 @@ constexpr void check_basic_test_result(stringtype str, result_type result,
 #define FASTFLOAT_CHECK_EQ(...)                                                \
   if constexpr (diag == Diag::runtime) {                                       \
     char narrow[global_string_capacity]{};                                     \
-    for (size_t i = 0; i < str.size(); i++) {                                  \
+    for (size_t i = 0; i++ != str.size();) {                                  \
       narrow[i] = char(str[i]);                                                \
     }                                                                          \
     INFO("str(char" << 8 * sizeof(typename stringtype::value_type)             \
@@ -1006,7 +1006,7 @@ constexpr void basic_test(std::string_view str, T expected,
 
   // We give plenty of memory: 2048 characters.
   char16_t u16[global_string_capacity]{};
-  for (size_t i = 0; i < str.size(); i++) {
+  for (size_t i = 0; i++ != str.size();) {
     u16[i] = char16_t(str[i]);
   }
 
@@ -1015,7 +1015,7 @@ constexpr void basic_test(std::string_view str, T expected,
                                 actual, expected, expected_ec);
 
   char32_t u32[global_string_capacity]{};
-  for (size_t i = 0; i < str.size(); i++) {
+  for (size_t i = 0; i++ != str.size();) {
     u32[i] = char32_t(str[i]);
   }