[numeric.special] (original) (raw)

17 Language support library [support]

17.3 Implementation properties [support.limits]

17.3.5 Class template numeric_limits [numeric.limits]

17.3.5.3 numeric_limits specializations [numeric.special]

All members shall be provided for all specializations.

However, many values are only required to be meaningful under certain conditions (for example,epsilon()is only meaningful ifis_integerisfalse).

Any value that is not “meaningful” shall be set to 0 orfalse.

[Example 1: namespace std { template<> class numeric_limits<float> { public: static constexpr bool is_specialized = true;static constexpr float min() noexcept { return 1.17549435E-38F; } static constexpr float max() noexcept { return 3.40282347E+38F; } static constexpr float lowest() noexcept { return -3.40282347E+38F; } static constexpr int digits = 24;static constexpr int digits10 = 6;static constexpr int max_digits10 = 9;static constexpr bool is_signed = true;static constexpr bool is_integer = false;static constexpr bool is_exact = false;static constexpr int radix = 2;static constexpr float epsilon() noexcept { return 1.19209290E-07F; } static constexpr float round_error() noexcept { return 0.5F; } static constexpr int min_exponent = -125;static constexpr int min_exponent10 = - 37;static constexpr int max_exponent = +128;static constexpr int max_exponent10 = + 38;static constexpr bool has_infinity = true;static constexpr bool has_quiet_NaN = true;static constexpr bool has_signaling_NaN = true;static constexpr float infinity() noexcept { return value; } static constexpr float quiet_NaN() noexcept { return value; } static constexpr float signaling_NaN() noexcept { return value; } static constexpr float denorm_min() noexcept { return min(); } static constexpr bool is_iec559 = true;static constexpr bool is_bounded = true;static constexpr bool is_modulo = false;static constexpr bool traps = true;static constexpr bool tinyness_before = true;static constexpr float_round_style round_style = round_to_nearest;};} — _end example_]

The specialization forboolshall be provided as follows:namespace std { template<> class numeric_limits<bool> { public: static constexpr bool is_specialized = true;static constexpr bool min() noexcept { return false; } static constexpr bool max() noexcept { return true; } static constexpr bool lowest() noexcept { return false; } static constexpr int digits = 1;static constexpr int digits10 = 0;static constexpr int max_digits10 = 0;static constexpr bool is_signed = false;static constexpr bool is_integer = true;static constexpr bool is_exact = true;static constexpr int radix = 2;static constexpr bool epsilon() noexcept { return 0; } static constexpr bool round_error() noexcept { return 0; } 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 bool infinity() noexcept { return 0; } static constexpr bool quiet_NaN() noexcept { return 0; } static constexpr bool signaling_NaN() noexcept { return 0; } static constexpr bool denorm_min() noexcept { return 0; } static constexpr bool is_iec559 = false;static constexpr bool is_bounded = true;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;};}