# Standard library header <cfloat>

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This header was originally in the C standard library as `<float.h>`.

This header is part of the type support library, in particular it's part of the C numeric limits interface.

### Macros

FLT_RADIX | the radix (integer base) used by the representation of all three floating-point types (macro constant)
DECIMAL_DIG (C++11) | conversion from long double to decimal with at least `DECIMAL_DIG` digits and back to long double is the identity conversion. : this is the decimal precision required to serialize/deserialize a long double (see also std::numeric_limits::max_digits10) (macro constant)

FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG
(C++17)

conversion from float/double/long double to decimal with at least `FLT_DECIMAL_DIG`/`DBL_DECIMAL_DIG`/`LDBL_DECIMAL_DIG` digits and back is the identity conversion. : this is the decimal precision required to serialize/deserialize a floating-point value (see also std::numeric_limits::max_digits10). Defined to at least 6, 10, and 10 respectively, or 9 for IEEE float and 17 for IEEE double.
(macro constant)

FLT_MINDBL_MINLDBL_MIN | minimum normalized positive value of float, double and long double respectively (macro constant)
FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN (C++17) | minimum positive value of float, double and long double respectively (macro constant)
FLT_MAXDBL_MAXLDBL_MAX | maximum value of float, double and long double respectively (macro constant)
FLT_EPSILONDBL_EPSILONLDBL_EPSILON | difference between 1.0 and the next representable value for float, double and long double respectively (macro constant)
FLT_DIGDBL_DIGLDBL_DIG | number of decimal digits that are guaranteed to be preserved in text -> float/double/long double -> text roundtrip without change due to rounding or overflow (see std::numeric_limits::digits10 for explanation) (macro constant)
FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG | number of base `FLT_RADIX` digits that can be represented without losing precision for float, double and long double respectively (macro constant)
FLT_MIN_EXPDBL_MIN_EXPLDBL_MIN_EXP | minimum negative integer such that `FLT_RADIX` raised by power one less than that integer is a normalized float, double and long double respectively (macro constant)
FLT_MIN_10_EXPDBL_MIN_10_EXPLDBL_MIN_10_EXP | minimum negative integer such that 10 raised by power one less than that integer is a normalized float, double and long double respectively (macro constant)
FLT_MAX_EXPDBL_MAX_EXPLDBL_MAX_EXP | maximum positive integer such that `FLT_RADIX` raised by power one more than that integer is a normalized float, double and long double respectively (macro constant)
FLT_MAX_10_EXPDBL_MAX_10_EXPLDBL_MAX_10_EXP | maximum positive integer such that 10 raised by power one more than that integer is a normalized float, double and long double respectively (macro constant)
FLT_ROUNDS | default rounding mode of floating-point arithmetics (macro constant)
FLT_EVAL_METHOD (C++11) | specifies in what precision all arithmetic operations are done (macro constant)
FLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM (C++17) | specifies whether the type supports subnormal (denormal) numbers: -1 indeterminable, 0 absent, 1 present (macro constant)

### Synopsis

    #define FLT_ROUNDS /*see definition*/
    #define FLT_EVAL_METHOD /*see definition*/
    #define FLT_HAS_SUBNORM /*see definition*/
    #define DBL_HAS_SUBNORM /*see definition*/
    #define LDBL_HAS_SUBNORM /*see definition*/
    #define FLT_RADIX /*see definition*/
    #define FLT_MANT_DIG /*see definition*/
    #define DBL_MANT_DIG /*see definition*/
    #define LDBL_MANT_DIG /*see definition*/
    #define FLT_DECIMAL_DIG /*see definition*/
    #define DBL_DECIMAL_DIG /*see definition*/
    #define LDBL_DECIMAL_DIG /*see definition*/
    #define DECIMAL_DIG /*see definition*/
    #define FLT_DIG /*see definition*/
    #define DBL_DIG /*see definition*/
    #define LDBL_DIG /*see definition*/
    #define FLT_MIN_EXP /*see definition*/
    #define DBL_MIN_EXP /*see definition*/
    #define LDBL_MIN_EXP /*see definition*/
    #define FLT_MIN_10_EXP /*see definition*/
    #define DBL_MIN_10_EXP /*see definition*/
    #define LDBL_MIN_10_EXP /*see definition*/
    #define FLT_MAX_EXP /*see definition*/
    #define DBL_MAX_EXP /*see definition*/
    #define LDBL_MAX_EXP /*see definition*/
    #define FLT_MAX_10_EXP /*see definition*/
    #define DBL_MAX_10_EXP /*see definition*/
    #define LDBL_MAX_10_EXP /*see definition*/
    #define FLT_MAX /*see definition*/
    #define DBL_MAX /*see definition*/
    #define LDBL_MAX /*see definition*/
    #define FLT_EPSILON /*see definition*/
    #define DBL_EPSILON /*see definition*/
    #define LDBL_EPSILON /*see definition*/
    #define FLT_MIN /*see definition*/
    #define DBL_MIN /*see definition*/
    #define LDBL_MIN /*see definition*/
    #define FLT_TRUE_MIN /*see definition*/
    #define DBL_TRUE_MIN /*see definition*/
    #define LDBL_TRUE_MIN /*see definition*/

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