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Allegro CL

ANSI Common Lisp   12 Numbers   12.2 Dictionary of Numbers

 12.2.4 float System Class

Class Precedence List:
float, real, number, t

Description:
A float is a mathematical rational (but not a Common Lisp rational) of the form s f be-p, where s is +1 or -1, the sign; b is an integer greater than 1, the base or radix of the representation; p is a positive integer, the precision (in base-b digits) of the float; f is a positive integer between bp-1 and bp-1 (inclusive), the significand; and e is an integer, the exponent. The value of p and the range of e depends on the implementation and on the type of float within that implementation. In addition, there is a floating-point zero; depending on the implementation, there can also be a "minus zero". If there is no minus zero, then 0.0 and -0.0 are both interpreted as simply a floating-point zero. (= 0.0 -0.0) is always true. If there is a minus zero, (eql -0.0 0.0) is false, otherwise it is true.

The types short-float, single-float, double-float, and long-float are subtypes of type float. Any two of them must be either disjoint types or the same type; if the same type, then any other types between them in the above ordering must also be the same type. For example, if the type single-float and the type long-float are the same type, then the type double-float must be the same type also.

Compound Type Specifier Kind:
Abbreviating.

Compound Type Specifier Syntax:
(float [lower-limit [upper-limit)]]

Compound Type Specifier Arguments:
lower-limit, upper-limit - interval designators for type float. The defaults for each of lower-limit and upper-limit is the symbol *.

Compound Type Specifier Description:
This denotes the floats on the interval described by lower-limit and upper-limit.