Collections and Data Structures

[Iteration](@id lib-collections-iteration)

Sequential iteration is implemented by the iterate function. The general for loop:

julia

for i in iter   # or  "for i = iter"
    # body
end

is translated into:

julia

next = iterate(iter)
while next !== nothing
    (i, state) = next
    # body
    next = iterate(iter, state)
end

The state object may be anything, and should be chosen appropriately for each iterable type. See the [manual section on the iteration interface](@ref man-interface-iteration) for more details about defining a custom iterable type.

@docs

Base.iterate
Base.IteratorSize
Base.IteratorEltype

Fully implemented by:

Constructors and Types

@docs

Base.AbstractRange
Base.OrdinalRange
Base.AbstractUnitRange
Base.StepRange
Base.UnitRange
Base.LinRange

General Collections

@docs

Base.isempty
Base.isdone
Base.empty!
Base.length
Base.checked_length

Fully implemented by:

Iterable Collections

@docs

Base.in
Base.:∉
Base.hasfastin
Base.eltype
Base.indexin
Base.unique
Base.unique!
Base.allunique
Base.allequal
Base.reduce(::Any, ::Any)
Base.reduce(::Any, ::AbstractArray)
Base.foldl(::Any, ::Any)
Base.foldr(::Any, ::Any)
Base.maximum
Base.maximum!
Base.minimum
Base.minimum!
Base.extrema
Base.extrema!
Base.argmax
Base.argmin
Base.findmax
Base.findmin
Base.findmax!
Base.findmin!
Base.sum
Base.sum!
Base.prod
Base.prod!
Base.any(::Any)
Base.any(::AbstractArray, ::Any)
Base.any!
Base.all(::Any)
Base.all(::AbstractArray, ::Any)
Base.all!
Base.count
Base.foreach
Base.map
Base.map!
Base.mapreduce(::Any, ::Any, ::Any)
Base.mapfoldl(::Any, ::Any, ::Any)
Base.mapfoldr(::Any, ::Any, ::Any)
Base.first
Base.last
Base.front
Base.tail
Base.step
Base.collect(::Any)
Base.collect(::Type, ::Any)
Base.filter
Base.filter!
Base.replace(::Any, ::Pair...)
Base.replace(::Base.Callable, ::Any)
Base.replace!
Base.rest
Base.split_rest

Indexable Collections

@docs

Base.getindex
Base.setindex!
Base.firstindex
Base.lastindex

Fully implemented by:

Partially implemented by:

Dictionaries

Dict is the standard dictionary. Its implementation uses hash as the hashing function for the key, and isequal to determine equality. Define these two functions for custom types to override how they are stored in a hash table.

IdDict is a special hash table where the keys are always object identities.

WeakKeyDict is a hash table implementation where the keys are weak references to objects, and thus may be garbage collected even when referenced in a hash table. Like Dict it uses hash for hashing and isequal for equality, unlike Dict it does not convert keys on insertion.

Dicts can be created by passing pair objects constructed with => to a Dict constructor: Dict("A"=>1, "B"=>2). This call will attempt to infer type information from the keys and values (i.e. this example creates a Dict{String, Int64}). To explicitly specify types use the syntax Dict{KeyType,ValueType}(...). For example, Dict{String,Int32}("A"=>1, "B"=>2).

Dictionaries may also be created with generators. For example, Dict(i => f(i) for i = 1:10).

Given a dictionary D, the syntax D[x] returns the value of key x (if it exists) or throws an error, and D[x] = y stores the key-value pair x => y in D (replacing any existing value for the key x). Multiple arguments to D[...] are converted to tuples; for example, the syntax D[x,y] is equivalent to D[(x,y)], i.e. it refers to the value keyed by the tuple (x,y).

@docs

Base.AbstractDict
Base.Dict
Base.IdDict
Base.WeakKeyDict
Base.ImmutableDict
Base.PersistentDict
Base.haskey
Base.get
Base.get!
Base.getkey
Base.delete!
Base.pop!(::Any, ::Any, ::Any)
Base.keys
Base.values
Base.pairs
Base.merge
Base.mergewith
Base.merge!
Base.mergewith!
Base.sizehint!
Base.keytype
Base.valtype

Fully implemented by:

Partially implemented by:

Set
BitSet
IdSet
[EnvDict](@ref Base.EnvDict)
Array
BitArray
[ImmutableDict](@ref Base.ImmutableDict)
[PersistentDict](@ref Base.PersistentDict)
Iterators.Pairs

Set-Like Collections

@docs

Base.AbstractSet
Base.Set
Base.BitSet
Base.IdSet
Base.union
Base.union!
Base.intersect
Base.setdiff
Base.setdiff!
Base.symdiff
Base.symdiff!
Base.intersect!
Base.issubset
Base.in!
Base.:⊈
Base.:⊊
Base.issetequal
Base.isdisjoint

Fully implemented by:

Partially implemented by:

Array

Dequeues

@docs

Base.push!
Base.pop!
Base.popat!
Base.pushfirst!
Base.popfirst!
Base.insert!
Base.deleteat!
Base.keepat!
Base.splice!
Base.resize!
Base.append!
Base.prepend!

Fully implemented by:

Vector (a.k.a. 1-dimensional Array)
BitVector (a.k.a. 1-dimensional BitArray)

Utility Collections

@docs

Base.Pair
Iterators.Pairs