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colinleachColin LeachColin Leach
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sets concept (exercism#815)
* WIP draft of sets concept * removed italics * sets moved from WIP --------- Co-authored-by: Colin Leach <[email protected]> Co-authored-by: Colin Leach <[email protected]>
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‎concepts/sets/.meta/config.json

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{
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"authors": [
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"colinleach"
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],
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"contributors": [],
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"blurb": "A Set in Julia is an unordered collection of unique entries, with fast algorithms for contains, union, intersection and difference operations."
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}

‎concepts/sets/about.md

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# About
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A [`Set`][set] is a collection of items with the following properties:
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- Unordered.
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- Entries are unique, so attempts to add duplicates are silently ignored.
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- Supports many of the operations common with mathematical sets.
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Create them with the `Set()` constructor, using any iterator as the parameter.
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```julia-repl
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julia> s1 = Set(1:4)
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Set{Int64} with 4 elements:
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4
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2
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3
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1
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```
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Add new elements with `push!()` (the same as with arrays), and remove them with `delete!()`.
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```julia-repl
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julia> push!(s1, 5)
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Set{Int64} with 5 elements:
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5
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4
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2
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3
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1
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# Duplicates are ignored
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julia> push!(s1, 3)
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Set{Int64} with 5 elements:
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5
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4
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2
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3
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1
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julia> delete!(s1, 5)
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Set{Int64} with 4 elements:
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4
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2
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3
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1
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julia> length(s1) # length counts entries, despite the non-sequential type
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4
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```
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## Set operations
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As with several other collection types, check membership with the `in` or `∈` operator (use `\in` then tab for the symbol).
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```julia-repl
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julia> 3 ∈ s1
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true
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```
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The following operations on pairs of Sets are supported (shortcuts to the operator symbol are shown in parentheses).
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- `union(A, B)` or `A ∪ B` (`\cup`): all entries in A or B or both.
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- `intersect(A, B)` or `A ∩ B` (`\cap`): all entries common to both A and B.
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- `setdiff(A, B)` (no symbol): entries in A but not in B.
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- `symdiff(A, B)` (no symbol): entries in either A or B but not both.
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- `issubset(A, B)` or `A ⊆ B` (`\subseteq`) or `B ⊇ A` (`\supseteq`): `true` if all entries in A are also in B.
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- `issetequal(A, B)` (no symbol): `true` if A and B contain exactly the same entries.
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- `isdisjoint(A, B)` (no symbol): `true` if A and B contain no entries in common (so intersect is empty).
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```julia-repl
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s1 = Set(1:4)
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s2 = Set(3:6)
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julia> s1 ∪ s2 # union
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Set{Int64} with 6 elements:
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5
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4
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6
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2
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3
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1
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julia> s1 ∩ s2 # intersect
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Set{Int64} with 2 elements:
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4
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3
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julia> setdiff(s1, s2)
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Set{Int64} with 2 elements:
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2
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1
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julia> symdiff(s1, s2)
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Set{Int64} with 4 elements:
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5
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6
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2
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1
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julia> s1 ⊇ s2 # issubset
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false
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```
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There are also mutating versions of many of these, with `!` added to the function name.
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See the [manual][set] for a full list of functions.
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[set]: https://docs.julialang.org/en/v1/base/collections/#Set-Like-Collections
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[union]: https://docs.julialang.org/en/v1/base/collections/#Base.union
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[intersect]: https://docs.julialang.org/en/v1/base/collections/#Base.intersect
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[setdiff]: https://docs.julialang.org/en/v1/base/collections/#Base.setdiff
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[symdiff]: https://docs.julialang.org/en/v1/base/collections/#Base.symdiff
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[issubset]: https://docs.julialang.org/en/v1/base/collections/#Base.issubset
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[issetequal]: https://docs.julialang.org/en/v1/base/collections/#Base.issetequal
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[isdisjoint]: https://docs.julialang.org/en/v1/base/collections/#Base.isdisjoint

‎concepts/sets/introduction.md

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# Introduction
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A [`Set`][set] is a collection of items with the following properties:
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- Unordered.
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- Entries are unique, so attempts to add duplicates are silently ignored.
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- Supports many of the operations common with mathematical sets.
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Create them with the `Set()` constructor, using any iterator as the parameter.
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```julia-repl
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julia> s1 = Set(1:4)
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Set{Int64} with 4 elements:
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4
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2
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3
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1
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```
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Add new elements with `push!()` (the same as with arrays), and remove them with `delete!()`.
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```julia-repl
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julia> push!(s1, 5)
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Set{Int64} with 5 elements:
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5
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4
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2
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3
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1
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# Duplicates are ignored
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julia> push!(s1, 3)
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Set{Int64} with 5 elements:
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5
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4
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2
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3
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1
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julia> delete!(s1, 5)
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Set{Int64} with 4 elements:
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4
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2
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3
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1
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julia> length(s1) # length counts entries, despite the non-sequential type
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4
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```
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## Set operations
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As with several other collection types, check membership with the `in` or `∈` operator (use `\in` then tab for the symbol).
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```julia-repl
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julia> 3 ∈ s1
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true
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```
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The following operations on pairs of Sets are supported (shortcuts to the operator symbol are shown in parentheses).
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- `union(A, B)` or `A ∪ B` (`\cup`): all entries in A or B or both.
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- `intersect(A, B)` or `A ∩ B` (`\cap`): all entries common to both A and B.
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- `setdiff(A, B)` (no symbol): entries in A but not in B.
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- `symdiff(A, B)` (no symbol): entries in either A or B but not both.
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- `issubset(A, B)` or `A ⊆ B` (`\subseteq`) or `B ⊇ A` (`\supseteq`): `true` if all entries in A are also in B.
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- `issetequal(A, B)` (no symbol): `true` if A and B contain exactly the same entries.
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- `isdisjoint(A, B)` (no symbol): `true` if A and B contain no entries in common (so intersect is empty).
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```julia-repl
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s1 = Set(1:4)
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s2 = Set(3:6)
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julia> s1 ∪ s2 # union
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Set{Int64} with 6 elements:
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5
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4
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6
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2
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3
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1
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julia> s1 ∩ s2 # intersect
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Set{Int64} with 2 elements:
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4
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3
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julia> setdiff(s1, s2)
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Set{Int64} with 2 elements:
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2
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1
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julia> symdiff(s1, s2)
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Set{Int64} with 4 elements:
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5
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6
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2
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1
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julia> s1 ⊇ s2 # issubset
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false
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```
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There are also mutating versions of many of these, with `!` added to the function name.
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See the [manual][set] for a full list of functions.
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[set]: https://docs.julialang.org/en/v1/base/collections/#Set-Like-Collections
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[union]: https://docs.julialang.org/en/v1/base/collections/#Base.union
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[intersect]: https://docs.julialang.org/en/v1/base/collections/#Base.intersect
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[setdiff]: https://docs.julialang.org/en/v1/base/collections/#Base.setdiff
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[symdiff]: https://docs.julialang.org/en/v1/base/collections/#Base.symdiff
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[issubset]: https://docs.julialang.org/en/v1/base/collections/#Base.issubset
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[issetequal]: https://docs.julialang.org/en/v1/base/collections/#Base.issetequal
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[isdisjoint]: https://docs.julialang.org/en/v1/base/collections/#Base.isdisjoint

‎concepts/sets/links.json

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[
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{
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"url": "https://docs.julialang.org/en/v1/base/collections/#Set-Like-Collections",
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"description": "Manual section on Sets and related collections."
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}
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]

‎config.json

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"slug": "vectors",
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"name": "Vectors"
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},
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{
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"uuid": "67dfc465-1a97-4bc1-9177-97e3a3ba55da",
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"slug": "sets",
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"name": "Sets"
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},
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{
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"uuid": "9babe703-1f5f-4f59-a4b2-349b8d461dd8",
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"slug": "conditionals",

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