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 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:

--

If there is only one, it is the type single-float. In this representation, an object is simultaneously of types single-float, double-float, short-float, and long-float.

--

Two internal representations can be arranged in either of the following ways:

*

Two types are provided: single-float and short-float. An object is simultaneously of types single-float, double-float, and long-float.

*

Two types are provided: single-float and double-float. An object is simultaneously of types single-float and short-float, or double-float and long-float.

--

Three internal representations can be arranged in either of the following ways:

*

Three types are provided: short-float, single-float, and double-float. An object can simultaneously be of type double-float and long-float.

*

Three types are provided: single-float, double-float, and long-float. An object can simultaneously be of types single-float and short-float.

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.

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