Java Reference
In-Depth Information
Table 4.1. Floating-point value set parameters
Where one or both extended-exponent value sets are supported by an implementation, then
for each supported extended-exponent value set there is a specific implementation-depend-
ent constant
K
, whose value is constrained by
Table 4.1
; this value
K
in turn dictates the
values for
E
min
and
E
max
.
Each of the four value sets includes not only the finite nonzero values that are ascribed to
it above, but also NaN values and the four values positive zero, negative zero, positive in-
finity, and negative infinity.
Note that the constraints in
Table 4.1
are designed so that every element of the float value
set is necessarily also an element of the float-extended-exponent value set, the double value
set, and the double-extended-exponent value set. Likewise, each element of the double
value set is necessarily also an element of the double-extended-exponent value set. Each
extended-exponent value set has a larger range of exponent values than the corresponding
standard value set, but does not have more precision.
The elements of the float value set are exactly the values that can be represented using
the single floating-point format defined in the IEEE 754 standard. The elements of the
double value set are exactly the values that can be represented using the double floating-
point format defined in the IEEE 754 standard. Note, however, that the elements of the
float-extended-exponent and double-extended-exponent value sets defined here do
not
cor-
respond to the values that can be represented using IEEE 754 single extended and double
extended formats, respectively.
The float, float-extended-exponent, double, and double-extended-exponent value sets are
not types. It is always correct for an implementation of the Java programming language to
use an element of the float value set to represent a value of type
float
; however, it may be
permissible in certain regions of code for an implementation to use an element of the float-
extended-exponent value set instead. Similarly, it is always correct for an implementation
to use an element of the double value set to represent a value of type
double
; however, it
