17 Language support library [support]

17.3 Implementation properties [support.limits]

17.3.5 Class template numeric_limits [numeric.limits]

17.3.5.1 General [numeric.limits.general]

1
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The numeric_limits class template provides a C++ program with information about various properties of the implementation's representation of the arithmetic types.
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namespace std { template<class T> class numeric_limits { public: static constexpr bool is_specialized = false; static constexpr T min() noexcept { return T(); } static constexpr T max() noexcept { return T(); } static constexpr T lowest() noexcept { return T(); } static constexpr int digits = 0; static constexpr int digits10 = 0; static constexpr int max_digits10 = 0; static constexpr bool is_signed = false; static constexpr bool is_integer = false; static constexpr bool is_exact = false; static constexpr int radix = 0; static constexpr T epsilon() noexcept { return T(); } static constexpr T round_error() noexcept { return T(); } static constexpr int min_exponent = 0; static constexpr int min_exponent10 = 0; static constexpr int max_exponent = 0; static constexpr int max_exponent10 = 0; static constexpr bool has_infinity = false; static constexpr bool has_quiet_NaN = false; static constexpr bool has_signaling_NaN = false; static constexpr T infinity() noexcept { return T(); } static constexpr T quiet_NaN() noexcept { return T(); } static constexpr T signaling_NaN() noexcept { return T(); } static constexpr T denorm_min() noexcept { return T(); } static constexpr bool is_iec559 = false; static constexpr bool is_bounded = false; static constexpr bool is_modulo = false; static constexpr bool traps = false; static constexpr bool tinyness_before = false; static constexpr float_round_style round_style = round_toward_zero; }; }
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For all members declared static constexpr in the numeric_limits template, specializations shall define these values in such a way that they are usable as constant expressions.
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For the numeric_limits primary template, all data members are value-initialized and all member functions return a value-initialized object.
[Note 1: 
This means all members have zero or false values unless numeric_limits is specialized for a type.
— end note]
4
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Specializations shall be provided for each arithmetic type, both floating-point and integer, including bool.
The member is_specialized shall be true for all such specializations of numeric_limits.
5
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The value of each member of a specialization of numeric_limits on a cv-qualified type cv T shall be equal to the value of the corresponding member of the specialization on the unqualified type T.
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Non-arithmetic standard types, such as complex<T>, shall not have specializations.