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ANSI Common Lisp 12 Numbers 12.2 Dictionary of Numbers
12.2.5 short-float, single-float, double-float, long-float |
Type |
- Supertypes:
-
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
- Description:
-
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 plog2b)
and the exponent size (also measured in "bits," computed as
log2(n+1), where n is the maximum exponent value) is recommended
to be at least as great
as the values in the next figure.
Each of the defined subtypes of type float might or might not have a minus zero.
Recommended Minimum Floating-Point Precision and Exponent Size
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 |
There can be fewer than four internal
representations for floats.
If there are fewer distinct representations, the following rules apply:
- Compound Type Specifier Kind:
-
Abbreviating.
- Compound Type Specifier Syntax:
-
(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]])
- Compound Type Specifier Arguments:
-
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 *.
- Compound Type Specifier Description:
-
Each of these denotes the set of floats of the indicated type
that are on the interval specified by the interval designators.
- Allegro CL Implementation Details:
-
None.
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