etl/docs/strings/to_arithmetic.md
John Wellbelove 4a88884b39
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---------

Co-authored-by: Roland Reichwein <Roland.Reichwein@bmw.de>
Co-authored-by: John Wellbelove <john.wellbelove@etlcpp.com>
Co-authored-by: John Wellbelove <john.wellbelove@etlcpp.co.uk>
2026-06-06 13:12:44 +01:00

8.8 KiB

title
to_arithmetic

{{< callout type="info">}} Header: to_arithmetic.h
{{< /callout >}}

Functions that will convert a text representation of an arithmetic type to a value.
Converts from binary, octal, decimal and hex integrals, and decimal floating point types.
Supports conversion from char, wchar_t, char8_t, char16_t, and char32_t strings.
The numeric strings must not contain leading or trailing non-numeric characters. It is the responsibility of the user to select the valid character range.
Integral types may be constexpr.

to_arithmetic_status

An ETL enum type that defines the following enumeration values.
The are the values that may be set as the error code in to_arithmetic_result.

Valid
Invalid_Radix
Invalid_Format
Invalid_Float
Signed_To_Unsigned
Overflow

to_arithmetic_result

The result type returned from etl::to_arithmetic.

template <typename TValue>
to_arithmetic_result

Types

value_type      TValue
error_type      etl::to_arithmetic_status
unexpected_type etl::unexpected<etl::to_arithmetic_status>

ETL_CONSTEXPR14
to_arithmetic_result()

Default constructor.


ETL_CONSTEXPR14
to_arithmetic_result(const to_arithmetic_result& other)

Copy constructor.


ETL_NODISCARD
ETL_CONSTEXPR14
bool has_value() const

Returns true if the result has a valid value.
If false then the value is undefined.


ETL_NODISCARD
ETL_CONSTEXPR14
operator bool() const

Returns true if the result has a valid value.
If false then the value is undefined.


ETL_NODISCARD
ETL_CONSTEXPR14
value_type value() const

Returns the value, if valid.
Otherwise undefined.


ETL_NODISCARD
ETL_CONSTEXPR14
operator value_type() const

Returns the value, if valid.
Otherwise undefined.


ETL_NODISCARD
ETL_CONSTEXPR14
error_type error() const

Returns the conversion status.
One of the following:-

Valid
Invalid_Radix
Invalid_Format
Invalid_Float
Signed_To_Unsigned
Overflow

ETL_CONSTEXPR14
to_arithmetic_result& operator =(value_type value)

Assign from a value_type.


ETL_CONSTEXPR14
to_arithmetic_result& operator =(unexpected_type status)

Assign from an unexpected_type.


to_arithmetic

Convert a string to an integral or floating point value.
Supports:
etl::string_view (etl::basic_string_view<TChar>) const pointer (to char, wchar_t, char8_t, char16_t, char32_t) + length
etl::string, etl::wstring, etl::u8string, etl::u16string, or etl::u32string.

template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const etl::basic_string_view<TChar>& view)

Text to integral or floating point from view and default decimal radix.


template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(etl::basic_string_view<TChar> view,
                                                const etl::radix::value_type  radix)

Text to integral from view and radix value type.
radix may be one of the following:-

etl::radix::binary
etl::radix::octal
etl::radix::decimal
etl::radix::hex

ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const etl::basic_string_view<TChar>& view, 
                                                const etl::private_basic_format_spec::base_spec& spec)

Text to integral from view and radix format spec.
spec may be one of the following:-

etl::bin
etl::oct
etl::dec
etl::hex

template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const TChar* cp, 
                                                size_t length)

Text to integral or floating point from pointer, length and default decimal radix.


template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const TChar* cp, 
                                                size_t length, 
                                                const etl::radix::value_type radix)

Text to integral from pointer, length and radix value type.
radix may be one of the following:-

etl::radix::binary
etl::radix::octal
etl::radix::decimal
etl::radix::hex

template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const TChar* cp, 
                                                size_t length, 
                                                const etl::private_basic_format_spec::base_spec& spec)

Text to integral from pointer, length and radix format spec.
spec may be one of the following:-

etl::bin
etl::oct
etl::dec
etl::hex

template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const etl::ibasic_string<TChar>& str)

Text to integral or floating point from string and default decimal radix.


template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const etl::ibasic_string<TChar>& str, 
                                                const etl::radix::value_type radix)

Text to integral from string and radix value type.
radix may be one of the following:-

etl::radix::binary
etl::radix::octal
etl::radix::decimal
etl::radix::hex

template <typename TValue, typename TChar>
ETL_NODISCARD
ETL_CONSTEXPR14
etl::to_arithmetic_result<TValue> to_arithmetic(const etl::ibasic_string<TChar>& str, 
                                                const etl::private_basic_format_spec::base_spec& spec)

Text to integral from string and radix format spec.
spec may be one of the following:-

etl::bin
etl::oct
etl::dec
etl::hex

Non-member functions

template <typename T>
ETL_CONSTEXPR14 bool operator ==(const etl::to_arithmetic_result<T>& lhs, 
                                 const etl::to_arithmetic_result<T>& rhs)

Equality test for etl::to_arithmetic_result


template <typename T, typename U>
ETL_CONSTEXPR14 bool operator ==(const etl::to_arithmetic_result<T>& lhs, 
                                 const U& rhs)

Equality test for etl::to_arithmetic_result


template <typename T, typename U>
ETL_CONSTEXPR14 bool operator ==(const T& lhs, 
                                 const etl::to_arithmetic_result<U>& rhs)

Equality test for etl::to_arithmetic_result


template <typename T>
ETL_CONSTEXPR14 bool operator !=(const etl::to_arithmetic_result<T>& lhs, 
                                 const etl::to_arithmetic_result<T>& rhs)

Inequality test for etl::to_arithmetic_result


template <typename T, typename U>
ETL_CONSTEXPR14 bool operator !=(const etl::to_arithmetic_result<T>& lhs, 
                                 const U& rhs)

Inequality test for etl::to_arithmetic_result


template <typename T, typename U>
ETL_CONSTEXPR14 bool operator !=(const T& lhs, 
                                 const etl::to_arithmetic_result<T>& rhs)

Inequality test for etl::to_arithmetic_result

Examples

Valid conversions

const char* BinaryText("1010011");
const etl::string<3> OctalText("123");
const etl::string<4> DecimalText(" 83 ");
const etl::string<2> HexText("85");
const etl::string<2> FloatText("-123e5");

// From char pointer to binary text. Format spec radix.
int v1 = etl::to_arithmetic<int>(BinaryText, strlen(BinaryText), etl::bin);

// From char pointer from octal text string. Radix spec value.
int v2 = etl::to_arithmetic<int>(OctalText.c_str(), OctalText.size(), etl::radix::octal);

// From view of decimal text string. Default base 10 radix.
etl::string_view view(DecimalText.data() + 1, DecimalText.data() + 3);
int v3 = etl::to_arithmetic<int>(view);

// From hex string. Base 16 radix.
int v4 = etl::to_arithmetic<int>(HexText, 16);

Invalid conversions

const etl::string<10> Text1("abcd");
const etl::string<10> Text2(" 83 ");
const etl::string<10> Text3("-83");
const etl::string<10> Text4("4294967296");
const etl::string<10> Text5("1.23E10000");

etl::to_arithmetic_result result;

result = etl::to_arithmetic<int32_t>(Text1, 5); // etl::to_arithmetic_status::Invalid_Radix

result = etl::to_arithmetic<int32_t>(Text1);    // etl::to_arithmetic_status::Invalid_Format

result = etl::to_arithmetic<int32_t>(Text2);    // etl::to_arithmetic_status::Invalid_Format

result = etl::to_arithmetic<uint32_t>(Text3);   // etl::to_arithmetic_status::Signed_To_Unsigned

result = etl::to_arithmetic<int32_t>(Text4);    // etl::to_arithmetic_status::Overflow

result = etl::to_arithmetic<float>(Text5);      // etl::to_arithmetic_status::Overflow