c++_std-numeric_limits极值接口

is_specialized

bool

true for all arithmetic types (i.e., those for which numeric_limits is specialized). false for all other types.

min()

T

Minimum finite value. For floating types with denormalization (variable number of exponent bits): minimum positive normalized value. Equivalent to CHAR_MIN, SCHAR_MIN, SHRT_MIN, INT_MIN, LONG_MIN, LLONG_MIN, FLT_MIN, DBL_MIN, LDBL_MIN or 0, depending on type.

max()

T

Maximum finite value. Equivalent to CHAR_MAX, SCHAR_MAX, UCHAR_MAX, SHRT_MAX, USHRT_MAX, INT_MAX, UINT_MAX, LONG_MAX, ULONG_MAX, LLONG_MAX, ULLONG_MAX, UINT_LEAST16_MAX, UINT_LEAST32_MAX, FLT_MAX, DBL_MAX or LDBL_MAX, depending on type.

lowest()

T

Minimum finite value. (since C++11) For integral types: the same as min(). For floating-point types: implementation-dependent; generally, the negative of max().

digits

int

For integer types: number of non-sign bits (radix base digits) in the representation. For floating types: number of digits (in radix base) in the mantissa (equivalent to FLT_MANT_DIG, DBL_MANT_DIG or LDBL_MANT_DIG).

digits10

int

Number of digits (in decimal base) that can be represented without change. Equivalent to FLT_DIG, DBL_DIG or LDBL_DIG for floating types.

max_digits10

int

Number of digits (in decimal base) required to ensure that values that differ are always differentiated.

is_signed

bool

true if type is signed.

is_integer

bool

测试目标类型是不是可以用整型来表示（比如char是1，float是0

is_exact

bool

true if type uses exact representations.

radix

int

For integer types: base of the representation. For floating types: base of the exponent of the representation (equivalent to FLT_RADIX).

epsilon()

T

返回目标数据类型能表示的最逼近1的正数和1的差的绝对值

round_error()

T

Measure of the maximum rounding error.

min_exponent

int

Minimum negative integer value such that radix raised to (min_exponent-1) generates a normalized floating-point number. Equivalent to FLT_MIN_EXP, DBL_MIN_EXP or LDBL_MIN_EXP for floating types.

min_exponent10

int

Minimum negative integer value such that 10 raised to that power generates a normalized floating-point number. Equivalent to FLT_MIN_10_EXP, DBL_MIN_10_EXP or LDBL_MIN_10_EXP for floating types.

max_exponent

int

Maximum integer value such that radix raised to (max_exponent-1) generates a representable finite floating-point number. Equivalent to FLT_MAX_EXP, DBL_MAX_EXP or LDBL_MAX_EXP for floating types.

max_exponent10

int

Maximum integer value such that 10 raised to that power generates a normalized finite floating-point number. Equivalent to FLT_MAX_10_EXP, DBL_MAX_10_EXP or LDBL_MAX_10_EXP for floating types.

has_infinity

bool

true if the type has a representation for positive infinity.

has_quiet_NaN

bool

true if the type has a representation for a quiet (non-signaling) "Not-a-Number".

has_signaling_NaN

bool

true if the type has a representation for a signaling "Not-a-Number".

has_denorm

float_denorm_style

测试目标类型是不是可以非规范化表示

has_denorm_loss

bool

测试所有类型是不是能测出因为非规范化而造成的精度损失（不是因为结果本身的不精确）

infinity()

T

检查目标类型的无限类型（如果支持无限表示）

quiet_NaN()

T

Representation of quiet (non-signaling) "Not-a-Number", if available.

signaling_NaN()

T

Representation of signaling "Not-a-Number", if available.

denorm_min()

T

Minimum positive denormalized value. For types not allowing denormalized values: same as min().

is_iec559

bool

测试目标类型是不是符合IEC559标准

is_bounded

bool

检查目标类型的取值是否有限

is_modulo

bool

true if the type is modulo. A type is modulo if it is possible to add two positive numbers and have a result that wraps around to a third number that is less.

traps

bool

true if trapping is implemented for the type.

tinyness_before

bool

true if tinyness is detected before rounding.

round_style

float_round_style

Rounding style. A type may have any of the following enum values: round_toward_zero, if it rounds toward zero. round_to_nearest, if it rounds to the nearest representable value. round_toward_infinity, if it rounds toward infinity. round_toward_neg_infinity, if it rounds toward negative infinity. round_indeterminate, if the rounding style is indeterminable at compile time.