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## 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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