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Merged
lemire merged 10 commits into from
Sep 18, 2025
Merged

Implemented multiplication of integer by a power of 10 #320

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7b8f045
implemented multiplication of integer by power of 10
toughengineer Sep 2, 2025
a134561
added missing `inline` specifiers
toughengineer Sep 2, 2025
cc90f24
added some tests
toughengineer Sep 2, 2025
6be07d6
inlining Clinger's fast path because why not,
toughengineer Sep 3, 2025
763558b
cleaned up tests
toughengineer Sep 3, 2025
20a7383
renamed the function, cleaned up return type
toughengineer Sep 5, 2025
6702cd4
added doc section in the README,
toughengineer Sep 5, 2025
e124635
added lacking overloads to avoid potential ambiguity
toughengineer Sep 5, 2025
7ae62ee
finally got the anti-ambiguity overloads right?
toughengineer Sep 5, 2025
0a23032
now finally got the anti-ambiguity overloads right, right?
toughengineer Sep 5, 2025
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added missing inline specifiers
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@toughengineer
toughengineer committed Sep 2, 2025
commit a134561e4b11a2c0dc708692591fb8297a4701b4
18 changes: 10 additions & 8 deletions include/fast_float/fast_float.h
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Original file line number Diff line number Diff line change
Expand Up @@ -58,14 +58,16 @@ from_chars_advanced(UC const *first, UC const *last, T &value,
* The implementation does not throw and does not allocate memory (e.g., with
* `new` or `malloc`).
*/
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<double>::value, double>::type
multiply_integer_and_power_of_10(uint64_t mantissa,
int decimal_exponent) noexcept;
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<double>::value, double>::type
multiply_integer_and_power_of_10(int64_t mantissa,
int decimal_exponent) noexcept;
FASTFLOAT_CONSTEXPR20 inline
typename std::enable_if<is_supported_float_type<double>::value,
double>::type
multiply_integer_and_power_of_10(uint64_t mantissa,
int decimal_exponent) noexcept;
FASTFLOAT_CONSTEXPR20 inline
typename std::enable_if<is_supported_float_type<double>::value,
double>::type
multiply_integer_and_power_of_10(int64_t mantissa,
int decimal_exponent) noexcept;

/**
* from_chars for integer types.
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35 changes: 20 additions & 15 deletions include/fast_float/parse_number.h
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Original file line number Diff line number Diff line change
Expand Up @@ -344,10 +344,11 @@ from_chars(UC const *first, UC const *last, T &value, int base) noexcept {
return from_chars_advanced(first, last, value, options);
}

FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<double>::value, double>::type
multiply_integer_and_power_of_10(uint64_t mantissa,
int decimal_exponent) noexcept {
FASTFLOAT_CONSTEXPR20 inline
typename std::enable_if<is_supported_float_type<double>::value,
double>::type
multiply_integer_and_power_of_10(uint64_t mantissa,
int decimal_exponent) noexcept {
double value;
if (clinger_fast_path_impl(mantissa, decimal_exponent, false, value))
return value;
Expand All @@ -358,10 +359,11 @@ multiply_integer_and_power_of_10(uint64_t mantissa,
return value;
}

FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<double>::value, double>::type
multiply_integer_and_power_of_10(int64_t mantissa,
int decimal_exponent) noexcept {
FASTFLOAT_CONSTEXPR20 inline
typename std::enable_if<is_supported_float_type<double>::value,
double>::type
multiply_integer_and_power_of_10(int64_t mantissa,
int decimal_exponent) noexcept {
const bool is_negative = mantissa < 0;
const uint64_t m = static_cast<uint64_t>(is_negative ? -mantissa : mantissa);

Expand All @@ -377,17 +379,20 @@ multiply_integer_and_power_of_10(int64_t mantissa,

// the following overloads are here to avoid surprising ambiguity for int,
// unsigned, etc.
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<double>::value, double>::type
multiply_integer_and_power_of_10(unsigned mantissa,
int decimal_exponent) noexcept {
FASTFLOAT_CONSTEXPR20 inline
typename std::enable_if<is_supported_float_type<double>::value,
double>::type
multiply_integer_and_power_of_10(unsigned mantissa,
int decimal_exponent) noexcept {
return multiply_integer_and_power_of_10(static_cast<uint64_t>(mantissa),
decimal_exponent);
}

FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<double>::value, double>::type
multiply_integer_and_power_of_10(int mantissa, int decimal_exponent) noexcept {
FASTFLOAT_CONSTEXPR20 inline
typename std::enable_if<is_supported_float_type<double>::value,
double>::type
multiply_integer_and_power_of_10(int mantissa,
int decimal_exponent) noexcept {
return multiply_integer_and_power_of_10(static_cast<int64_t>(mantissa),
decimal_exponent);
}
Expand Down