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Added template overloads for integer_times_pow10() #328

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Added template overloads for integer_times_pow10() #328

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13345ca
added template overload for `integer_times_pow10()`
toughengineer Sep 18, 2025
01e5057
added tests + some refactoring
toughengineer Sep 18, 2025
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14 changes: 14 additions & 0 deletions include/fast_float/fast_float.h
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,20 @@ integer_times_pow10(uint64_t mantissa, int decimal_exponent) noexcept;
FASTFLOAT_CONSTEXPR20 inline double
integer_times_pow10(int64_t mantissa, int decimal_exponent) noexcept;

/**
* This function is a template overload of `integer_times_pow10()`
* that returns a floating-point value of type `T` that is one of
* supported floating-point types (e.g. `double`, `float`).
*/
template <typename T>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value, T>::type
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This is kinda ugly, an option is to add a macro similar to FASTFLOAT_ENABLE_IF along the lines of

#define FASTFLOAT_ENABLE_IF_T(T, ...) typename std::enable_if<(__VA_ARGS__), T>::type

Then even the macro FASTFLOAT_ENABLE_IF can be reimplemented (DRY and whatnot):

#define FASTFLOAT_ENABLE_IF(...) FASTFLOAT_ENABLE_IF_T(int, __VA_ARGS__)

integer_times_pow10(uint64_t mantissa, int decimal_exponent) noexcept;
template <typename T>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value, T>::type
integer_times_pow10(int64_t mantissa, int decimal_exponent) noexcept;

/**
* from_chars for integer types.
*/
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57 changes: 46 additions & 11 deletions include/fast_float/parse_number.h
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Original file line number Diff line number Diff line change
Expand Up @@ -344,44 +344,79 @@ from_chars(UC const *first, UC const *last, T &value, int base) noexcept {
return from_chars_advanced(first, last, value, options);
}

FASTFLOAT_CONSTEXPR20 inline double
integer_times_pow10(uint64_t mantissa, int decimal_exponent) noexcept {
double value;
template <typename T>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value, T>::type
integer_times_pow10(uint64_t mantissa, int decimal_exponent) noexcept {
T value;
if (clinger_fast_path_impl(mantissa, decimal_exponent, false, value))
return value;

adjusted_mantissa am =
compute_float<binary_format<double>>(decimal_exponent, mantissa);
compute_float<binary_format<T>>(decimal_exponent, mantissa);
to_float(false, am, value);
return value;
}

FASTFLOAT_CONSTEXPR20 inline double
integer_times_pow10(int64_t mantissa, int decimal_exponent) noexcept {
template <typename T>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value, T>::type
integer_times_pow10(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);

double value;
T value;
if (clinger_fast_path_impl(m, decimal_exponent, is_negative, value))
return value;

adjusted_mantissa am =
compute_float<binary_format<double>>(decimal_exponent, m);
adjusted_mantissa am = compute_float<binary_format<T>>(decimal_exponent, m);
to_float(is_negative, am, value);
return value;
}

FASTFLOAT_CONSTEXPR20 inline double
integer_times_pow10(uint64_t mantissa, int decimal_exponent) noexcept {
return integer_times_pow10<double>(mantissa, decimal_exponent);
}

FASTFLOAT_CONSTEXPR20 inline double
integer_times_pow10(int64_t mantissa, int decimal_exponent) noexcept {
return integer_times_pow10<double>(mantissa, decimal_exponent);
}

// the following overloads are here to avoid surprising ambiguity for int,
// unsigned, etc.
template <typename T, typename Int>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value &&
std::is_integral<Int>::value &&
!std::is_signed<Int>::value,
T>::type
integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
return integer_times_pow10<T>(static_cast<uint64_t>(mantissa),
decimal_exponent);
}

template <typename T, typename Int>
FASTFLOAT_CONSTEXPR20
typename std::enable_if<is_supported_float_type<T>::value &&
std::is_integral<Int>::value &&
std::is_signed<Int>::value,
T>::type
integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
return integer_times_pow10<T>(static_cast<int64_t>(mantissa),
decimal_exponent);
}

template <typename Int>
FASTFLOAT_CONSTEXPR20 inline typename std::enable_if<
FASTFLOAT_CONSTEXPR20 typename std::enable_if<
std::is_integral<Int>::value && !std::is_signed<Int>::value, double>::type
integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
return integer_times_pow10(static_cast<uint64_t>(mantissa), decimal_exponent);
}

template <typename Int>
FASTFLOAT_CONSTEXPR20 inline typename std::enable_if<
FASTFLOAT_CONSTEXPR20 typename std::enable_if<
std::is_integral<Int>::value && std::is_signed<Int>::value, double>::type
integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
return integer_times_pow10(static_cast<int64_t>(mantissa), decimal_exponent);
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