Documentation:OCLOperators insertAt

insertAt ( index : Integer, object : T) : Sequence(T)

Returns a Sequence containing self with object inserted at the *index* position.

Expression	Result
Sequence{'a', 'b'}->insertAt(0, 'c')	invalid
Sequence{'a', 'b'}->insertAt(1, 'c')	Sequence{'c', 'a', 'b'}
Sequence{'a', 'b'}->insertAt(3, 'c')	Sequence{'a', 'b', 'c'}
Sequence{'a', 'b'}->insertAt(4, 'c')	invalid

Insert an object in a specific place in a collection or association. <collection>.insertAt(<position>, <object>)

Used when you don't want a new object at the end using add.

For associations, it only makes sense to use insertAt on ordered associations.

• Note that the position is 1-based, not 0.

See also: Association