8.3 Set constructors

When a set-type constant must be entered in an expression, a set constructor must be given. In essence this is the same thing as when a type is deﬁned, only there is no identiﬁer to identify the set with. A set constructor is a comma separated list of expressions, enclosed in square brackets.

_________________________________________________________________________________________________________ Set constructors
--set constructor-[--|-------------]-------------------------------
-|-set group--
----,-----

--set group-expression--|-------------------------------------------
-.. -expression--
___________________________________________________________________

All set groups and set elements must be of the same ordinal type. The empty set is denoted by [], and it can be assigned to any type of set. A set group with a range [A..Z] makes all values in the range a set element. If the ﬁrst range speciﬁer has a bigger ordinal value than the second the set is empty, e.g., [Z..A] denotes an empty set. The following are valid set constructors:

[today,tomorrow]
[Monday..Friday,Sunday]
[ 2, 3*2, 6*2, 9*2 ]
[’A’..’Z’,’a’..’z’,’0’..’9’]

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