to_arithmetic.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2022 John Wellbelove
 
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#ifndef ETL_TO_ARITHMETIC_INCLUDED
#define ETL_TO_ARITHMETIC_INCLUDED
 
#include "platform.h"
#include "type_traits.h"
#include "integral_limits.h"
#include "limits.h"
#include "string_view.h"
#include "basic_string.h"
#include "format_spec.h"
#include "radix.h"
#include "string_utilities.h"
#include "iterator.h"
#include "bit.h"
#include "smallest.h"
#include "absolute.h"
#include "expected.h"
#include "math.h"
 
#include <math.h>
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  struct to_arithmetic_status
  {
    enum enum_type
    {
      Valid,
      Invalid_Radix,
      Invalid_Format,
      Invalid_Float,
      Signed_To_Unsigned,
      Overflow
    };
 
    ETL_DECLARE_ENUM_TYPE(to_arithmetic_status, int)
    ETL_ENUM_TYPE(Valid,              "Valid")
    ETL_ENUM_TYPE(Invalid_Radix,      "Invalid Radix")
    ETL_ENUM_TYPE(Invalid_Format,     "Invalid Format")
    ETL_ENUM_TYPE(Invalid_Float,      "Invalid Float")
    ETL_ENUM_TYPE(Signed_To_Unsigned, "Signed To Unsigned")
    ETL_ENUM_TYPE(Overflow,           "Overflow")
    ETL_END_ENUM_TYPE
  };
 
  //***************************************************************************
  //***************************************************************************
  template<typename TValue>
  class to_arithmetic_result
  {
  public:
 
    typedef TValue                                     value_type;
    typedef etl::to_arithmetic_status                  error_type;
    typedef etl::unexpected<etl::to_arithmetic_status> unexpected_type;
 
    //*******************************************
    //*******************************************
    ETL_CONSTEXPR14
    to_arithmetic_result()
      : conversion_value(static_cast<value_type>(0))
      , conversion_status(error_type::Valid)
    {
    }
 
    //*******************************************
    //*******************************************
    ETL_CONSTEXPR14
    to_arithmetic_result(const to_arithmetic_result& other)
      : conversion_value(other.conversion_value)
      , conversion_status(other.conversion_status)
    {
    }
 
    //*******************************************
    //*******************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14
    bool has_value() const
    {
      return (conversion_status.error() == error_type::Valid);
    }
 
    //*******************************************
    //*******************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14
    operator bool() const
    {
      return has_value();
    }
 
    //*******************************************
    //*******************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14
    value_type value() const
    {
      return conversion_value;
    }
 
    //*******************************************
    //*******************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14
    operator value_type() const
    {
      return value();
    }
 
    //*******************************************
    //*******************************************
    ETL_NODISCARD
    ETL_CONSTEXPR14
    error_type error() const
    {
      return etl::to_arithmetic_status(conversion_status.error());
    }
 
    //*******************************************
    //*******************************************
    ETL_CONSTEXPR14
    to_arithmetic_result& operator =(value_type value_)
    {
      conversion_value = value_;
 
      return *this;
    }
 
    //*******************************************
    //*******************************************
    ETL_CONSTEXPR14
    to_arithmetic_result& operator =(unexpected_type status_)
    {
      conversion_status = status_;
 
      return *this;
    }
 
  private:
 
    value_type      conversion_value;
    unexpected_type conversion_status;
  };
 
  namespace private_to_arithmetic
  {
    template <typename T = void>
    struct char_statics
    {
      static ETL_CONSTANT char Positive_Char = '+';
      static ETL_CONSTANT char Negative_Char = '-';
      static ETL_CONSTANT char Radix_Point1_Char = '.';
      static ETL_CONSTANT char Radix_Point2_Char = ',';
      static ETL_CONSTANT char Exponential_Char = 'e';
    };
 
    template <typename T>
    ETL_CONSTANT char char_statics<T>::Positive_Char;
 
    template <typename T>
    ETL_CONSTANT char char_statics<T>::Negative_Char;
 
    template <typename T>
    ETL_CONSTANT char char_statics<T>::Radix_Point1_Char;
 
    template <typename T>
    ETL_CONSTANT char char_statics<T>::Radix_Point2_Char;
 
    template <typename T>
    ETL_CONSTANT char char_statics<T>::Exponential_Char;
 
    struct char_constant : char_statics<>
    {
    };
 
    //*******************************************
    ETL_NODISCARD
    inline
    ETL_CONSTEXPR14
    bool is_valid(char c, etl::radix::value_type radix)
    {
      switch (radix)
      {
        case etl::radix::binary:
        {
          return (c >= '0') && (c <= '1');
        }
 
        case etl::radix::octal:
        {
          return (c >= '0') && (c <= '7');
        }
 
        case etl::radix::decimal:
        {
          return (c >= '0') && (c <= '9');
        }
 
        case etl::radix::hexadecimal:
        {
          return ((c >= '0') && (c <= '9')) || ((c >= 'a') && (c <= 'f'));
        }
 
        default:
        {
          return false;
        }
      }
    }
 
    //*******************************************
    ETL_NODISCARD
    inline
    ETL_CONSTEXPR14
    char digit_value(char c, etl::radix::value_type radix)
    {
      switch (radix)
      {
        case etl::radix::binary:
        case etl::radix::octal:
        case etl::radix::decimal:
        {
          return c - '0';
        }
 
        case etl::radix::hexadecimal:
        {
          if ((c >= '0') && (c <= '9'))
          {
            return c - '0';
          }
          else
          {
            return (c - 'a') + 10;
          }
        }
 
        default:
        {
          return 0;
        }
      }
    }
 
    //*******************************************
    ETL_NODISCARD
    inline 
    ETL_CONSTEXPR14
    char to_lower(char c)
    {
      if ((c >= 'A') && (c <= 'Z'))
      {
        c += 32;
      }
 
      return c;
    }
 
    //*******************************************
    template <typename TChar>
    ETL_NODISCARD
    ETL_CONSTEXPR14
    char convert(TChar c)
    {
      return to_lower(static_cast<char>(c));
    }
 
    //***************************************************************************
    //***************************************************************************
    template <typename TChar>
    ETL_NODISCARD
    ETL_CONSTEXPR14
    bool check_and_remove_sign_prefix(etl::basic_string_view<TChar>& view)
    {
      if (!view.empty())
      {
        // Check for prefix.
        const char c = convert(view[0]);
        const bool has_positive_prefix = (c == char_constant::Positive_Char);
        const bool has_negative_prefix = (c == char_constant::Negative_Char);
 
        // Step over the prefix, if present.
        if (has_positive_prefix || has_negative_prefix)
        {
          view.remove_prefix(1);
          return has_negative_prefix;
        }
      }
 
      return false;
    }
 
    //***************************************************************************
    //***************************************************************************
    ETL_NODISCARD
    inline
    ETL_CONSTEXPR14
    bool is_valid_radix(const etl::radix::value_type radix)
    {
      return (radix == etl::radix::binary)  ||
             (radix == etl::radix::octal)   ||
             (radix == etl::radix::decimal) ||
             (radix == etl::radix::hexadecimal);
    }
 
    //***************************************************************************
    //***************************************************************************
    template <typename TValue>
    struct integral_accumulator
    {
      //*********************************
      ETL_CONSTEXPR14
      integral_accumulator(etl::radix::value_type radix_, TValue maximum_)
        : radix(radix_)
        , maximum(maximum_)
        , integral_value(0)
        , conversion_status(to_arithmetic_status::Valid)
      {
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      bool add(const char c)
      {
        bool is_success      = false;
        bool is_not_overflow = false;
 
        const bool is_valid_char = is_valid(c, radix);
 
        if (is_valid_char)
        {
          TValue old_value = integral_value;
          integral_value *= radix;
 
          // No multiplication overflow?
          is_not_overflow = ((integral_value / radix) == old_value);
 
          if (is_not_overflow)
          {
            const char digit = digit_value(c, radix);
 
            // No addition overflow?
            is_not_overflow = ((maximum - digit) >= integral_value);
 
            if ((maximum - digit) >= integral_value)
            {
              integral_value += digit;
              is_success = true;
            }
          }
        }
 
        // Check the status of the conversion.
        if (is_valid_char == false)
        {
          conversion_status = to_arithmetic_status::Invalid_Format;
        }
        else if (is_not_overflow == false)
        {
          conversion_status = to_arithmetic_status::Overflow;
        }
 
        return is_success;
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      bool has_value() const
      {
        return conversion_status == to_arithmetic_status::Valid;
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      TValue value() const
      {
        return integral_value;
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      to_arithmetic_status status() const
      {
        return conversion_status;
      }
 
    private:
 
      etl::radix::value_type radix;
      TValue maximum;
      TValue integral_value;
      to_arithmetic_status conversion_status;
    };
 
    //***************************************************************************
    //***************************************************************************
    struct floating_point_accumulator
    {
      //*********************************
      ETL_CONSTEXPR14
      floating_point_accumulator()
        : divisor(1)
        , floating_point_value(0)
        , is_negative_mantissa(false)
        , is_negative_exponent(false)
        , expecting_sign(true)
        , exponent_value(0)
        , state(Parsing_Integral)
        , conversion_status(to_arithmetic_status::Valid)
      {
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      bool add(char c)
      {
        bool is_success = true;
 
        switch (state)
        {
          //***************************
          case Parsing_Integral:
          {
            if (expecting_sign && ((c == char_constant::Positive_Char) || (c == char_constant::Negative_Char)))
            {
              is_negative_mantissa = (c == char_constant::Negative_Char);
              expecting_sign = false;
            }
            // Radix point?
            else if ((c == char_constant::Radix_Point1_Char) || (c == char_constant::Radix_Point2_Char))
            {
              expecting_sign = false;
              state = Parsing_Fractional;
            }
            // Exponential?
            else if (c == char_constant::Exponential_Char)
            {
              expecting_sign = true;
              state = Parsing_Exponential;
            }
            else if (is_valid(c, etl::radix::decimal))
            {
              const char digit = digit_value(c, etl::radix::decimal);
              floating_point_value *= 10;
              is_negative_mantissa ? floating_point_value -= digit : floating_point_value += digit;
              conversion_status = to_arithmetic_status::Valid;
              expecting_sign = false;
            }
            else
            {
              conversion_status = to_arithmetic_status::Invalid_Format;
              is_success = false;
            }
            break;
          }
 
          //***************************
          case Parsing_Fractional:
          {
            // Radix point?
            if ((c == char_constant::Radix_Point1_Char) || (c == char_constant::Radix_Point2_Char))
            {
              conversion_status = to_arithmetic_status::Invalid_Format;
              is_success = false;
            }
            // Exponential?
            else if (c == char_constant::Exponential_Char)
            {
              expecting_sign = true;
              state = Parsing_Exponential;
            }
            else if (is_valid(c, etl::radix::decimal))
            {
              const char digit = digit_value(c, etl::radix::decimal);
              divisor *= 10;
              long double fraction = digit / divisor;
              is_negative_mantissa ? floating_point_value -= fraction : floating_point_value += fraction;
              conversion_status = to_arithmetic_status::Valid;
            }
            else
            {
              conversion_status = to_arithmetic_status::Invalid_Format;
              is_success = false;
            }
            break;
          }
 
          //***************************
          case Parsing_Exponential:
          {
            if (expecting_sign && ((c == char_constant::Positive_Char) || (c == char_constant::Negative_Char)))
            {
              is_negative_exponent = (c == char_constant::Negative_Char);
              expecting_sign = false;
            }
            // Radix point?
            else if ((c == char_constant::Radix_Point1_Char) || (c == char_constant::Radix_Point2_Char) || (c == char_constant::Exponential_Char))
            {
              conversion_status = to_arithmetic_status::Invalid_Format;
              is_success = false;
            }
            else if (is_valid(c, etl::radix::decimal))
            {
              const char digit = digit_value(c, etl::radix::decimal);
              exponent_value *= etl::radix::decimal;
              is_negative_exponent ? exponent_value -= digit : exponent_value += digit;
            }
            else
            {
              conversion_status = to_arithmetic_status::Invalid_Format;
              is_success = false;
            }
            break;
          }
 
          //***************************
          default:
          {
            is_success = false;
            break;
          }
        }
 
        return is_success;
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      bool has_value() const
      {
        return (conversion_status == to_arithmetic_status::Valid);
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      long double value() const
      {
        return floating_point_value;
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      to_arithmetic_status status() const
      {
        return conversion_status;
      }
 
      //*********************************
      ETL_NODISCARD
      ETL_CONSTEXPR14
      int exponent() const
      {
        return exponent_value;
      }
 
    private:
 
      enum
      {
        Parsing_Integral,
        Parsing_Fractional,
        Parsing_Exponential
      };
 
      long double divisor;
      long double floating_point_value;
      bool is_negative_mantissa;
      bool is_negative_exponent;
      bool expecting_sign;
      int  exponent_value;
      int  state;
      to_arithmetic_status conversion_status;
    };
 
    //***************************************************************************
    // Define an unsigned accumulator type that is at least as large as TValue.
    //***************************************************************************
    template <size_t Bits>
    struct accumulator_type_select;
 
    template <>
    struct accumulator_type_select<8U>
    {
      typedef uint32_t type;
    };
 
    template <>
    struct accumulator_type_select<16U>
    {
      typedef uint32_t type;
    };
 
    template <>
    struct accumulator_type_select<32U>
    {
      typedef uint32_t type;
    };
 
#if ETL_USING_64BIT_TYPES
    template <>
    struct accumulator_type_select<64U>
    {
      typedef uint64_t type;
    };
#endif
 
    //***************************************************************************
    //***************************************************************************
    template <typename TChar, typename TAccumulatorType>
    ETL_NODISCARD
    ETL_CONSTEXPR14
    etl::to_arithmetic_result<TAccumulatorType> to_arithmetic_integral(const etl::basic_string_view<TChar>& view,
                                                                       const etl::radix::value_type         radix,
                                                                       const TAccumulatorType               maximum)
    {
      etl::to_arithmetic_result<TAccumulatorType>   accumulator_result;
      typedef typename etl::unexpected<etl::to_arithmetic_status> unexpected_type;
 
      typename etl::basic_string_view<TChar>::const_iterator       itr     = view.begin();
      const typename etl::basic_string_view<TChar>::const_iterator itr_end = view.end();
 
      integral_accumulator<TAccumulatorType> accumulator(radix, maximum);
 
      while ((itr != itr_end) && accumulator.add(convert(*itr)))
      {
        // Keep looping until done or an error occurs.
        ++itr;
      }
 
      if (accumulator.has_value())
      {
        accumulator_result = accumulator.value();
      }
      else
      {
        accumulator_result = unexpected_type(accumulator.status());
      }
 
      return accumulator_result;
    }
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(etl::basic_string_view<TChar> view,
                  const etl::radix::value_type  radix)
  {
    using namespace etl::private_to_arithmetic;
 
    typedef etl::to_arithmetic_result<TValue>     result_type;
    typedef typename result_type::unexpected_type unexpected_type;
 
    result_type result;    
 
    if (is_valid_radix(radix))
    {
      // Is this a negative number?
      const bool is_negative = check_and_remove_sign_prefix(view);
 
      if (view.empty())
      {
        result = unexpected_type(to_arithmetic_status::Invalid_Format);
      }
      else
      {
        // Make sure we're not trying to put a negative value into an unsigned type.
        if (is_negative && etl::is_unsigned<TValue>::value)
        {
          result = unexpected_type(to_arithmetic_status::Signed_To_Unsigned);
        }
        else
        {
          const bool is_decimal = (radix == etl::radix::decimal);
 
          // Select the type we use for the accumulator.
          typedef typename accumulator_type_select<etl::integral_limits<TValue>::bits>::type accumulator_type;
 
          // Find the maximum absolute value for the type value we're trying to convert to.
          const accumulator_type maximum = is_negative ? etl::absolute_unsigned(etl::integral_limits<TValue>::min)
                                                       : is_decimal ? etl::integral_limits<TValue>::max
                                                                    : etl::integral_limits<typename etl::make_unsigned<TValue>::type>::max;
          // Do the conversion.
          etl::to_arithmetic_result<accumulator_type> accumulator_result = to_arithmetic_integral<TChar>(view, radix, maximum);
 
          result = unexpected_type(accumulator_result.error());
 
          // Was it successful?
          if (accumulator_result.has_value())
          {
            typedef typename etl::make_unsigned<TValue>::type uvalue_t;
            const uvalue_t uvalue = static_cast<uvalue_t>(accumulator_result.value());
 
            // Convert from the accumulator type to the desired type.
            result = (is_negative ? static_cast<TValue>(0) - uvalue : etl::bit_cast<TValue>(uvalue));
          }
        }
      }
    }
    else
    {
      result = unexpected_type(to_arithmetic_status::Invalid_Radix);
    }
 
    return result;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const etl::basic_string_view<TChar>& view)
  {
    return etl::to_arithmetic<TValue, TChar>(view, etl::radix::decimal);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const etl::basic_string_view<TChar>& view, const typename etl::private_basic_format_spec::base_spec& spec)
  {
    return etl::to_arithmetic<TValue, TChar>(view, spec.base);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const TChar* cp, size_t length, const etl::radix::value_type radix)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(cp, length), radix);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const TChar* cp, size_t length)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(cp, length), etl::radix::decimal);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const TChar* cp, size_t length, const typename etl::private_basic_format_spec::base_spec& spec)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(cp, length), spec.base);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const etl::ibasic_string<TChar>& str, const etl::radix::value_type radix)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(str), radix);;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
    ETL_CONSTEXPR14
    typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const etl::ibasic_string<TChar>& str)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(str), etl::radix::decimal);;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_integral<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const etl::ibasic_string<TChar>& str, const typename etl::private_basic_format_spec::base_spec& spec)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(str), spec);;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_floating_point<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(etl::basic_string_view<TChar> view)
  {
    using namespace etl::private_to_arithmetic;
 
    typedef etl::to_arithmetic_result<TValue>     result_type;
    typedef typename result_type::unexpected_type unexpected_type;
 
    result_type result;
 
    if (view.empty())
    {
      result = unexpected_type(to_arithmetic_status::Invalid_Format);
    }
    else
    {
      floating_point_accumulator accumulator;
 
      typename etl::basic_string_view<TChar>::const_iterator itr           = view.begin();
      const typename etl::basic_string_view<TChar>::const_iterator itr_end = view.end();
 
      while ((itr != itr_end) && accumulator.add(convert(*itr)))
      {
        // Keep looping until done or an error occurs.
        ++itr;
      }
 
      result = unexpected_type(accumulator.status());
 
      if (result.has_value())
      {
        TValue value = static_cast<TValue>(accumulator.value());
        int exponent = accumulator.exponent();
 
        value *= pow(static_cast<TValue>(10.0), static_cast<TValue>(exponent));
 
        // Check that the result is a valid floating point number.
        if (etl::is_infinity(value))
        {
          result = unexpected_type(to_arithmetic_status::Overflow);
        }
        else if (etl::is_nan(value))
        {
          result = unexpected_type(to_arithmetic_status::Invalid_Float);
        }
        else
        {
          result = value;
        }
      }
    }
 
    return result;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_floating_point<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const TChar* cp, size_t length)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(cp, length));
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14
  typename etl::enable_if<etl::is_floating_point<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const TChar* cp)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(cp, etl::strlen<TChar>(cp)));
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TValue, typename TChar>
  ETL_NODISCARD
  ETL_CONSTEXPR14 
  typename etl::enable_if<etl::is_floating_point<TValue>::value, etl::to_arithmetic_result<TValue> >::type
    to_arithmetic(const etl::ibasic_string<TChar>& str)
  {
    return etl::to_arithmetic<TValue, TChar>(etl::basic_string_view<TChar>(str));
  }
}
 
//***************************************************************************
//***************************************************************************
template <typename T>
ETL_CONSTEXPR14 bool operator ==(const etl::to_arithmetic_result<T>& lhs, const etl::to_arithmetic_result<T>& rhs)
{
  if (lhs.has_value() && rhs.has_value())
  {
    return (lhs.value() == rhs.value());
  }
  else
  {
    return (lhs.status() == rhs.status());
  }
}
 
//***************************************************************************
//***************************************************************************
template <typename T, typename U>
ETL_CONSTEXPR14 bool operator ==(const etl::to_arithmetic_result<T>& lhs, const U& rhs)
{
  return bool(lhs) ? lhs.value() == rhs : false;
}
 
//***************************************************************************
//***************************************************************************
template <typename T, typename U>
ETL_CONSTEXPR14 bool operator ==(const T& lhs, const etl::to_arithmetic_result<U>& rhs)
{
  return bool(rhs) ? rhs.value() == lhs : false;
}
 
//***************************************************************************
//***************************************************************************
template <typename T>
ETL_CONSTEXPR14 bool operator !=(const etl::to_arithmetic_result<T>& lhs, const etl::to_arithmetic_result<T>& rhs)
{
  return !(lhs == rhs);
}
 
//***************************************************************************
//***************************************************************************
template <typename T, typename U>
ETL_CONSTEXPR14 bool operator !=(const etl::to_arithmetic_result<T>& lhs, const U& rhs)
{
  return !(lhs == rhs);
}
 
//***************************************************************************
//***************************************************************************
template <typename T, typename U>
ETL_CONSTEXPR14 bool operator !=(const T& lhs, const etl::to_arithmetic_result<T>& rhs)
{
  return !(lhs == rhs);
}
 
#endif