Node: short-float, Next: rational (System Class), Previous: float (System Class), Up: Numbers Dictionary
short-float: short-float, float,
real,
number, t
single-float: single-float, float,
real,
number, t
double-float: double-float, float,
real,
number, t
long-float: long-float, float,
real,
number, t
For the four defined subtypes of type float, it is true that intermediate between the type short-float and the type long-float are the type single-float and the type double-float. The precise definition of these categories is implementation-defined. The precision (measured in "bits", computed as p\log_2b) and the exponent size (also measured in "bits," computed as \log_2(n+1), where n is the maximum exponent value) is recommended to be at least as great as the values in Figure 12-11. Each of the defined subtypes of type float might or might not have a minus zero.
Format Minimum Precision Minimum Exponent Size __________________________________________________ Short 13 bits 5 bits Single 24 bits 8 bits Double 50 bits 8 bits Long 50 bits 8 bits Figure 12--11: Recommended Minimum Floating-Point Precision and Exponent Size
There can be fewer than four internal representations for floats. If there are fewer distinct representations, the following rules apply:
Abbreviating.
(short-float
{[short-lower-limit [short-upper-limit]]})
(single-float
{[single-lower-limit [single-upper-limit]]})
(double-float
{[double-lower-limit [double-upper-limit]]})
(long-float
{[long-lower-limit [long-upper-limit]]})
short-lower-limit, short-upper-limit--interval designators for type short-float. The defaults for each of lower-limit and upper-limit is the symbol *.
single-lower-limit, single-upper-limit--interval designators for type single-float. The defaults for each of lower-limit and upper-limit is the symbol *.
double-lower-limit, double-upper-limit--interval designators for type double-float. The defaults for each of lower-limit and upper-limit is the symbol *.
long-lower-limit, long-upper-limit--interval designators for type long-float. The defaults for each of lower-limit and upper-limit is the symbol *.
Each of these denotes the set of floats of the indicated type that are on the interval specified by the interval designators.