numeric_limits
Standard C++ Library
Copyright 1996, Rogue Wave Software, Inc.
NAME
numeric_limits - A class for representing information about scalar
types.
SPECIALIZATIONS
numeric_limits<float>
numeric_limits<double>
numeric_limits<long double>
numeric_limits<short>
numeric_limits<unsigned short>
numeric_limits<int>
numeric_limits<unsigned int>
numeric_limits<long>
numeric_limits<unsigned long>
numeric_limits<char>
numeric_limits<wchar_t>
numeric_limits<unsigned char>
numeric_limits<signed char>
numeric_limits<bool>
SYNOPSIS
#include <limits>
template <class T>
class numeric_limits ;
DESCRIPTION
numeric_limits is a class for representing information about scalar
types. Specializations are provided for each fundamental type, both
floating point and integer, including bool.
This class encapsulates information that is contained in the
<climits> and <cfloat> headers, as well as providing additional
information that is not contained in any existing C or C++ header.
Not all of the information provided by members is meaningful for all
specializations of numeric_limits. Any value which is not
meaningful for a particular type is set to 0 or false.
INTERFACE
template <class T>
class numeric_limits {
public:
// General -- meaningful for all specializations.
static const bool is_specialized ;
static T min ();
static T max ();
static const int radix ;
static const int digits ;
static const int digits10 ;
static const bool is_signed ;
static const bool is_integer ;
static const bool is_exact ;
static const bool traps ;
static const bool is_modulo ;
static const bool is_bounded ;
// Floating point specific.
static T epsilon ();
static T round_error ();
static const int min_exponent10 ;
static const int max_exponent10 ;
static const int min_exponent ;
static const int max_exponent ;
static const bool has_infinity ;
static const bool has_quiet_NaN ;
static const bool has_signaling_NaN ;
static const bool is_iec559 ;
static const bool has_denorm ;
static const bool tinyness_before ;
static const float_round_style round_style ;
static T denorm_min ();
static T infinity ();
static T quiet_NaN ();
static T signaling_NaN ();
};
enum float_round_style {
round_indeterminate = -1,
round_toward_zero = 0,
round_to_nearest = 1,
round_toward_infinity = 2,
round_toward_neg_infinity = 3
};
MEMBER FIELDS AND FUNCTIONS
static T
denorm_min ();
Returns the minimum denormalized value. Meaningful for all
floating point types. For types that do not allow denormalized
values, this method must return the minimum normalized value.
static const int
digits ;
Number of radix digits which can be represented without change.
For built-in integer types, digits will usually be the number of
non-sign bits in the representation. For floating point types,
digits is the number of radix digits in the mantissa. This member
is meaningful for all specializations that declare is_bounded to
be true.
static const int
digits10 ;
Number of base 10 digits that can be represented without change.
Meaningful for all specializations that declare is_bounded to be
true.
static T
epsilon ();
Returns the machine epsilon (the difference between 1 and the least
value greater than 1 that is representable). This function is
meaningful for floating point types only.
static const bool
has_denorm ;
This field is true if the type allows denormalized values
(variable number of exponent bits). It is meaningful for
floating point types only.
static const bool
has_infinity ;
This field is true if the type has a representation for positive
infinity. It is meaningful for floating point types only. This
field must be true for any type claiming conformance to IEC 559.
static const bool
has_quiet_NaN ;
This field is true is the type has a representation for a quiet
(non-signaling) "Not a Number". It is meaningful for floating
point types only and must be true for any type claiming
conformance to IEC 559.
static const bool
has_signaling_NaN ;
This field is true if the type has a representation for a
signaling "Not a Number". It is meaningful for floating point
types only, and must be true for any type claiming conformance
to IEC 559.
static T
infinity ();
Returns the representation of positive infinity, if available.
This member function is meaningful for only those
specializations that declare has_infinity to be true.
Required for any type claiming conformance to IEC 559.
static const bool
is_bounded ;
This field is true if the set of values representable by the type
is finite. All built-in C types are bounded; this member
would be false for arbitrary precision types.
static const bool
is_exact ;
This static member field is true if the type uses an exact
representation. All integer types are exact, but not vice
versa. For example, rational and fixed-exponent representations
are exact but not integer. This member is meaningful for all
specializations.
static const bool
is_iec559 ;
This member is true if and only if the type adheres to the IEC
559 standard. It is meaningful for floating point types
only. Must be true for any type claiming conformance to IEC 559.
static const bool
is_integer ;
This member is true if the type is integer. This member is
meaningful for all specializations.
static const bool
is_modulo ;
This field is true if the type is modulo. Generally, this is
false for floating types, true for unsigned integers, and true
for signed integers on most machines. A type is modulo if it is
possible to add two positive numbers, and have a result that wraps
around to a third number, which is less.
static const bool
is_signed ;
This member is true if the type is signed. This member is
meaningful for all specializations.
static const bool
is_specialized ;
Indicates whether numeric_limits has been specialized for type T.
This flag must be true for all specializations of numeric_limits.
In the default numeric_limits<T> template, this flag must be
false.
static T
max ();
Returns the maximum finite value. This function is meaningful
for all specializations that declare is_bounded to be
true.
static const int
max_exponent ;
Maximum positive integer such that the radix raised to that power
is in range. This field is meaningful for floating point types
only.
static const int
max_exponent10 ;
Maximum positive integer such that 10 raised to that power is in
range. This field is meaningful for floating point types only.
static T
min ();
Returns the minimum finite value. For floating point types with
denormalization, min()must return the minimum normalized value.
The minimum denormalized value is provided by denorm_min(). This
function is meaningful for all specializations that declare
is_bounded to be true.
static const int
min_exponent ;
Minimum negative integer such that the radix raised to that power
is in range. This field is meaningful for floating point types
only.
static const int
min_exponent10 ;
Minimum negative integer such that 10 raised to that power is in
range. This field is meaningful for floating point types only.
static T
quiet_NaN ();
Returns the representation of a quiet "Not a Number", if
available. This function is meaningful only for those
specializations that declare has_quiet_NaN to be true. This field
is required for any type claiming conformance to IEC 559.
static const int
radix ;
For floating types, specifies the base or radix of the exponent
representation (often 2). For integer types, this member must
specify the base of the representation. This field is meaningful
for all specializations.
static T
round_error ();
Returns the measure of the maximum rounding error. This function
is meaningful for floating point types only.
static const float_round_style
round_style ;
The rounding style for the type. Specializations for integer
types must return round_toward_zero. This is meaningful for all
floating point types.
static T
signaling_NaN();
Returns the representation of a signaling "Not a Number", if
available. This function is meaningful for only those
specializations that declare has_signaling_NaN to be true. This
function must be meaningful for any type claiming conformance to
IEC 559.
static const bool
tinyness_before ;
This member is true if tinyness is detected before rounding. It
is meaningful for floating point types only.
static const bool
traps ;
This field is true if trapping is implemented for this type.
The traps field is meaningful for all specializations.
EXAMPLE
//
// limits.cpp
//
#include <limits>
int main()
{
numeric_limits<float> float_info;
if (float_info.is_specialized && float_info.has_infinity)
{
// get value of infinity
float finfinity=float_info.infinity();
}
return 0;
}
WARNING
The specializations for wide chars and bool will only be available
if your compiler has implemented them as real types and not
simulated them with typedefs.
SEE ALSO
IEEE Standard for Binary Floating-Point Arithmetic, 345 East 47th
Street, New York, NY 10017
Language Independent Arithmetic (LIA-1)
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
