Structure operators (STRUCT, [])

The term structure is used in the platform to refer to the classes whose objects consist of a collection of other objects in a fixed order. The platform supports two operators for working with structures:

Operator	Name	Description	Example	Result
STRUCT	Creation	Creates a property that takes a list of operands and returns a structure consisting of the objects passed	STRUCT('a', 1)	STRUCT('a', 1)
[ ]	Access	Creates a property that takes an operand with a fixed integer and returns an object of the structure specified in the first operand with a number equal to the specified integer	STRUCT('a',1)[2]	1

Structures support comparison operations which are executed sequentially for each object included in the structure.

A structure exists only when all of its objects exist: if any of them is NULL, the whole structure is NULL, and the access operator returns NULL for a NULL structure.

Determining the result class

The result class is determined as:

Operator	Result
STRUCT	A structure of the operand classes, in the same order
[ ]	The class of the structure object at the specified position

Language

To create a property that creates a structure the STRUCT operator is used.

To create a property that returns an object from the structure the [ ] operator is used.

Examples

objectStruct(a, b) = STRUCT(a, f(b));
stringStruct() = STRUCT(1, 'two', 3.0);

CLASS Letter;
attachment1 = DATA FILE (Letter);
attachment2 = DATA FILE (Letter);
letterAttachments (Letter l) = STRUCT(attachment1(l), attachment2(l));
secondAttachment(Letter l) = letterAttachments(l)[2]; // returns attachment2