Array elements are ordered, but can contain duplicates, that is, the same value can occur at different indices. In a dictionary, keys have to be unique, but the values do not, and the keys are not ordered. If you want a collection where order does not matter, but where the elements have to be unique, then use a Set. Creating a set is easy as this:

// code in Chapter 5\sets.jl:
s = Set({11, 14, 13, 7, 14, 11})

The Set() function creates an empty set. The preceding line returns Set{Int64}({7,14,13,11}), where the duplicates have been eliminated. From v0.4 onwards, the {} notation with sets is deprecated; you should use s = Set(Any[11, 14, 13, 7, 14, 11]). In the accompanying code file, the latest version is used.

The operations from the set theory are also defined for s1 = Set({11, 25}) and s2 = Set({25, 3.14}) as follows: