In short, sub-binding types are usually used to intercept a "small" range that meets the needs of program operation from a "large" data definition range.

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.