<float.h>

Include the standard header <float.h> to determine various properties of floating-point type representations. The standard header <float.h> is available even in a freestanding implementation.

You can test the values of any of the integer macros except FLT_ROUNDS in an if directive. (The macros expand to #if expressions.) All other macros defined in this header expand to floating-point constant expressions.

Some target environments can change the rounding and error-reporting properties of floating-point type representations while the program is running.

#define FLT_RADIX <#if expression >= 2>
#define FLT_ROUNDS <integer rvalue>
#define FLT_EVAL_METHOD <#if expression> [added with C99]
#define DECIMAL_DIG <#if expression> >= 10 [added with C99]

#define DBL_DIG <#if expression >= 10>
#define DBL_EPSILON <double constant <= 10^(-9)>
#define DBL_MANT_DIG <#if expression>
#define DBL_MAX <double constant >= 10^37>
#define DBL_MAX_10_EXP <#if expression >= 37>
#define DBL_MAX_EXP <#if expression>
#define DBL_MIN <double constant <= 10^(-37)>
#define DBL_MIN_10_EXP <#if expression <= -37>
#define DBL_MIN_EXP <#if expression>

#define FLT_DIG <#if expression >= 6>
#define FLT_EPSILON <float constant <= 10^(-5)>
#define FLT_MANT_DIG <#if expression>
#define FLT_MAX <float constant >= 10^37>
#define FLT_MAX_10_EXP <#if expression >= 37>
#define FLT_MAX_EXP <#if expression>
#define FLT_MIN <float constant <= 10^(-37)>
#define FLT_MIN_10_EXP <#if expression <= -37>
#define FLT_MIN_EXP <#if expression>

#define LDBL_DIG <#if expression >= 10>
#define LDBL_EPSILON <long double constant <= 10^(-9)>
#define LDBL_MANT_DIG <#if expression>
#define LDBL_MAX <long double constant >= 10^37>
#define LDBL_MAX_10_EXP <#if expression >= 37>
#define LDBL_MAX_EXP <#if expression>
#define LDBL_MIN <long double constant <= 10^(-37)>
#define LDBL_MIN_10_EXP <#if expression <= -37>
#define LDBL_MIN_EXP <#if expression>

DBL_DIG

#define DBL_DIG <#if expression >= 10>

The macro yields the precision in decimal digits for type double.

DBL_EPSILON

#define DBL_EPSILON <double constant <= 10^(-9)>

The macro yields the smallest X of type double such that 1.0 + X != 1.0.

DBL_MANT_DIG

#define DBL_MANT_DIG <#if expression>

The macro yields the number of mantissa digits, base FLT_RADIX, for type double.

DBL_MAX

#define DBL_MAX <double constant >= 10^37>

The macro yields the largest finite representable value of type double.

DBL_MAX_10_EXP

#define DBL_MAX_10_EXP <#if expression >= 37>

The macro yields the maximum integer X, such that 10^X is a finite representable value of type double.

DBL_MAX_EXP

#define DBL_MAX_EXP <#if expression>

The macro yields the maximum integer X, such that FLT_RADIX^(X - 1) is a finite representable value of type double.

DBL_MIN

#define DBL_MIN <double constant <= 10^(-37)>

The macro yields the smallest normalized, finite representable value of type double.

DBL_MIN_10_EXP

#define DBL_MIN_10_EXP <#if expression <= -37>

The macro yields the minimum integer X such that 10^X is a normalized, finite representable value of type double.

DBL_MIN_EXP

#define DBL_MIN_EXP <#if expression>

The macro yields the minimum integer X such that FLT_RADIX^(X - 1) is a normalized, finite representable value of type double.

DECIMAL_DIG

#define DECIMAL_DIG <#if expression >= 10> [added with C99]

The macro yields the minimum number of decimal digits needed to represent all the significant digits for type long double.

FLT_DIG

#define FLT_DIG <#if expression >= 6>

The macro yields the precision in decimal digits for type float.

FLT_EPSILON

#define FLT_EPSILON <float constant <= 10^(-5)>

The macro yields the smallest X of type float such that 1.0 + X != 1.0.

FLT_EVAL_METHOD

#define FLT_EVAL_METHOD <#if expression> [added with C99]

The macro yields a value that describes the evaluation mode for floating-point operations. The values are:

• -1 if the mode is indeterminate
• 0 if no promotions occur
• 1 if float values promote to double
• 2 if float and double values promote to long double

An implementation can define additional negative values for this macro.

FLT_MANT_DIG

#define FLT_MANT_DIG <#if expression>

The macro yields the number of mantissa digits, base FLT_RADIX, for type float.

FLT_MAX

#define FLT_MAX <float constant >= 10^37>

The macro yields the largest finite representable value of type float.

FLT_MAX_10_EXP

#define FLT_MAX_10_EXP <#if expression >= 37>

The macro yields the maximum integer X, such that 10^X is a finite representable value of type float.

FLT_MAX_EXP

#define FLT_MAX_EXP <#if expression>

The macro yields the maximum integer X, such that FLT_RADIX^(X - 1) is a finite representable value of type float.

FLT_MIN

#define FLT_MIN <float constant <= 10^(-37)>

The macro yields the smallest normalized, finite representable value of type float.

FLT_MIN_10_EXP

#define FLT_MIN_10_EXP <#if expression <= -37>

The macro yields the minimum integer X, such that 10^X is a normalized, finite representable value of type float.

FLT_MIN_EXP

#define FLT_MIN_EXP <#if expression>

The macro yields the minimum integer X, such that FLT_RADIX^(X - 1) is a normalized, finite representable value of type float.

FLT_RADIX

#define FLT_RADIX <#if expression >= 2>

The macro yields the radix of all floating-point representations.

FLT_ROUNDS

#define FLT_ROUNDS <integer rvalue>

The macro yields a value that describes the current rounding mode for floating-point operations. Note that the target environment can change the rounding mode while the program executes. How it does so, however, is not specified. The values are:

• -1 if the mode is indeterminate
• 0 if rounding is toward zero
• 1 if rounding is to nearest representable value
• 2 if rounding is toward positive infinity
• 3 if rounding is toward negative infinity

An implementation can define additional values for this macro.

LDBL_DIG

#define LDBL_DIG <#if expression >= 10>

The macro yields the precision in decimal digits for type long double.

LDBL_EPSILON

#define LDBL_EPSILON <long double constant <= 10^(-9)>

The macro yields the smallest X of type long double such that 1.0 + X != 1.0.

LDBL_MANT_DIG

#define LDBL_MANT_DIG <#if expression>

The macro yields the number of mantissa digits, base FLT_RADIX, for type long double.

LDBL_MAX

#define LDBL_MAX <long double constant >= 10^37>

The macro yields the largest finite representable value of type long double.

LDBL_MAX_10_EXP

#define LDBL_MAX_10_EXP <#if expression >= 37>

The macro yields the maximum integer X, such that 10^X is a finite representable value of type long double.

LDBL_MAX_EXP

#define LDBL_MAX_EXP <#if expression>

The macro yields the maximum integer X, such that FLT_RADIX^(X - 1) is a finite representable value of type long double.

LDBL_MIN

#define LDBL_MIN <long double constant <= 10^(-37)>

The macro yields the smallest normalized, finite representable value of type long double.

LDBL_MIN_10_EXP

#define LDBL_MIN_10_EXP <#if expression <= -37>

The macro yields the minimum integer X, such that 10^X is a normalized, finite representable value of type long double.

LDBL_MIN_EXP

#define LDBL_MIN_EXP <#if expression>

The macro yields the minimum integer X, such that FLT_RADIX^(X - 1) is a normalized, finite representable value of type long double.

See also the Table of Contents and the Index.

Copyright © 1989-2002 by P.J. Plauger and Jim Brodie. All rights reserved.