Sub-boundary types are usually defined as follows:
Type? Sub-binding type identifier = low lower limit .. high upper limit
The definition of sub-boundary data requires that it must be of the same "sequential" data type, that is, the data is divided into sizes and sorted. There are many such data types, such as common integer, char, enumeration and so on.
Examples are as follows:
type
Tag? =? 18..45; ? //Define the age subboundary
TPasswordChars? =? A .. z'; ? //Defines a sub-boundary type that uses only uppercase letters.
TColors? =? (red,? Blue? Green? Yellow? Oranges? Purple? White? Black); ? {? Enumeration}
TMyColors? =? Green (surname); Green .. white; ? {? Define a child binding type in the enumeration that ranges from green to white.