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  ANSI Common Lisp   12 Numbers   12.1 Number Concepts

12.1.6 Interval Designators

The compound type specifier form of the numeric type specifiers permit the user to specify an interval on the real number line which describe a subtype of the type which would be described by the corresponding atomic type specifier. A subtype of some type T is specified using an ordered pair of objects called interval designators for type T.

The first of the two interval designators for type T can be any of the following:

  • a number N of type T

    This denotes a lower inclusive bound of N. That is, elements of the subtype of T will be greater than or equal to N.

  • a singleton list whose element is a number M of type T

    This denotes a lower exclusive bound of M. That is, elements of the subtype of T will be greater than M.

  • the symbol *

    This denotes the absence of a lower bound on the interval.

The second of the two interval designators for type T can be any of the following:

  • a number N of type T

    This denotes an upper inclusive bound of N. That is, elements of the subtype of T will be less than or equal to N.

  • a singleton list whose element is a number M of type T

    This denotes an upper exclusive bound of M. That is, elements of the subtype of T will be less than M.

  • the symbol *

    This denotes the absence of an upper bound on the interval.


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