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union!

union!(s, iterable)

Union each element of iterable into set s in-place.

Examples

1. Merge two sets in-place:

   julia> set1 = Set([1, 2, 3]);
   julia> set2 = Set([3, 4, 5]);
   julia> union!(set1, set2)
   Set{Int64} with 5 elements:
   4
   2
   3
   5
   1

   This example merges set2 into set1 in-place, resulting in a set with all unique elements from both sets.

2. Add elements from an array to a set:

   julia> set = Set([1, 2, 3]);
   julia> arr = [3, 4, 5];
   julia> union!(set, arr)
   Set{Int64} with 5 elements:
   4
   2
   3
   5
   1

   It adds the elements from the array arr to the set set in-place.

3. Merge multiple sets into one:

   julia> set1 = Set([1, 2, 3]);
   julia> set2 = Set([3, 4, 5]);
   julia> set3 = Set([5, 6, 7]);
   julia> union!(set1, set2, set3)
   Set{Int64} with 7 elements:
   4
   2
   3
   5
   7
   6
   1

   This example demonstrates how to merge multiple sets (set2 and set3) into set1 in-place.

Common mistake example:

julia> set = Set([1, 2, 3]);
julia> union!(set, [3, 4, 5])
ERROR: MethodError: no method matching union!(::Set{Int64}, ::Array{Int64,1})

In this example, the union! function is called with a set and an array. However, union! expects the second argument to be an iterable, not an array directly. To fix this, wrap the array with [] to create an iterable:

julia> set = Set([1, 2, 3]);
julia> union!(set, [3, 4, 5])
Set{Int64} with 5 elements:
  4
  2
  3
  5
  1

See Also

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