Collection - Sequence (Ordered)


A sequence is an abstract collection:

  • of non-unique element
  • where order matters - ie (A,B) is not equal to (B,A)

non-unique means that it allows duplicate member (the same element/value may occur more than once).

Order matter for equivalence Duplicate is allowed Collection Type
false false set
false true Bag
true false OrderedSet
true true Sequence


  • (M, A, R, Y) is a sequence of letters with the letter M first and Y last.
  • (M, A, R, Y) differs from (A, R, M, Y)


Rank / Index

The position of an element in a sequence is its rank or index.



A finite sequence is called a list


A infinite sequence is called a stream and is generally read through a iterator pattern.

Access type

It's a data structures with no or slow random access.

Documentation / Reference

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