• Reference Guide


An instance of the union of types is a value of one of the types composing a union. If, for example, a union is composed of an integer (Int) and a string (String), an instance of the union may be either an integer or a string.
A union may be either bound or unbound. A bound union is determined by a list of types representing permitted values of the union instance. Instances of an unbound union may acquire values of any type. The number of enumerated types of a bound union is limited to 254 in the current version.
Using union as the element type in a sequence or array effectively releases the requirement for elements to be of the same type.


Union(TYPE1, TYPE2, ... TYPEn)
where TYPE1, TYPE2, ... TYPEn are types composing the union (i.e. permitted instance types).