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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.

*Copyright 1996, The Harlequin Group Limited. All Rights Reserved.*