Collections and Data Structures

# Collections and Data Structures

## Iteration

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

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

is translated into:

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 for more details about defining a custom iterable type.

Base.iterateFunction.
iterate(iter [, state]) -> Union{Nothing, Tuple{Any, Any}}

Advance the iterator to obtain the next element. If no elements remain, nothing should be returned. Otherwise, a 2-tuple of the next element and the new iteration state should be returned.

source
IteratorSize(itertype::Type) -> IteratorSize

Given the type of an iterator, return one of the following values:

• SizeUnknown() if the length (number of elements) cannot be determined in advance.
• HasLength() if there is a fixed, finite length.
• HasShape{N}() if there is a known length plus a notion of multidimensional shape (as for an array). In this case N should give the number of dimensions, and the axes function is valid for the iterator.
• IsInfinite() if the iterator yields values forever.

The default value (for iterators that do not define this function) is HasLength(). This means that most iterators are assumed to implement length.

This trait is generally used to select between algorithms that pre-allocate space for their result, and algorithms that resize their result incrementally.

julia> Base.IteratorSize(1:5)
Base.HasShape{1}()

julia> Base.IteratorSize((2,3))
Base.HasLength()
source
IteratorEltype(itertype::Type) -> IteratorEltype

Given the type of an iterator, return one of the following values:

• EltypeUnknown() if the type of elements yielded by the iterator is not known in advance.
• HasEltype() if the element type is known, and eltype would return a meaningful value.

HasEltype() is the default, since iterators are assumed to implement eltype.

This trait is generally used to select between algorithms that pre-allocate a specific type of result, and algorithms that pick a result type based on the types of yielded values.

julia> Base.IteratorEltype(1:5)
Base.HasEltype()
source

Fully implemented by:

## Constructors and Types

AbstractRange{T}

Supertype for ranges with elements of type T. UnitRange and other types are subtypes of this.

source
OrdinalRange{T, S} <: AbstractRange{T}

Supertype for ordinal ranges with elements of type T with spacing(s) of type S. The steps should be always-exact multiples of oneunit, and T should be a "discrete" type, which cannot have values smaller than oneunit. For example, Integer or Date types would qualify, whereas Float64 would not (since this type can represent values smaller than oneunit(Float64). UnitRange, StepRange, and other types are subtypes of this.

source
AbstractUnitRange{T} <: OrdinalRange{T, T}

Supertype for ranges with a step size of oneunit(T) with elements of type T. UnitRange and other types are subtypes of this.

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Base.StepRangeType.
StepRange{T, S} <: OrdinalRange{T, S}

Ranges with elements of type T with spacing of type S. The step between each element is constant, and the range is defined in terms of a start and stop of type T and a step of type S. Neither T nor S should be floating point types. The syntax a:b:c with b > 1 and a, b, and c all integers creates a StepRange.

Examples

julia> collect(StepRange(1, Int8(2), 10))
5-element Array{Int64,1}:
1
3
5
7
9

julia> typeof(StepRange(1, Int8(2), 10))
StepRange{Int64,Int8}

julia> typeof(1:3:6)
StepRange{Int64,Int64}
source
Base.UnitRangeType.
UnitRange{T<:Real}

A range parameterized by a start and stop of type T, filled with elements spaced by 1 from start until stop is exceeded. The syntax a:b with a and b both Integers creates a UnitRange.

Examples

julia> collect(UnitRange(2.3, 5.2))
3-element Array{Float64,1}:
2.3
3.3
4.3

julia> typeof(1:10)
UnitRange{Int64}
source
Base.LinRangeType.
LinRange{T}

A range with len linearly spaced elements between its start and stop. The size of the spacing is controlled by len, which must be an Int.

Examples

julia> LinRange(1.5, 5.5, 9)
9-element LinRange{Float64}:
1.5,2.0,2.5,3.0,3.5,4.0,4.5,5.0,5.5
source

## General Collections

Base.isemptyFunction.
isempty(collection) -> Bool

Determine whether a collection is empty (has no elements).

Examples

julia> isempty([])
true

julia> isempty([1 2 3])
false
source
Base.empty!Function.
empty!(collection) -> collection

Remove all elements from a collection.

Examples

julia> A = Dict("a" => 1, "b" => 2)
Dict{String,Int64} with 2 entries:
"b" => 2
"a" => 1

julia> empty!(A);

julia> A
Dict{String,Int64} with 0 entries
source
Base.lengthFunction.
length(collection) -> Integer

Return the number of elements in the collection.

Use lastindex to get the last valid index of an indexable collection.

Examples

julia> length(1:5)
5

julia> length([1, 2, 3, 4])
4

julia> length([1 2; 3 4])
4
source

Fully implemented by:

## Iterable Collections

Base.inFunction.
in(item, collection) -> Bool
∈(item, collection) -> Bool
∋(collection, item) -> Bool

Determine whether an item is in the given collection, in the sense that it is == to one of the values generated by iterating over the collection. Returns a Bool value, except if item is missing or collection contains missing but not item, in which case missing is returned (three-valued logic, matching the behavior of any and ==).

Some collections follow a slightly different definition. For example, Sets check whether the item isequal to one of the elements. Dicts look for key=>value pairs, and the key is compared using isequal. To test for the presence of a key in a dictionary, use haskey or k in keys(dict). For these collections, the result is always a Bool and never missing.

Examples

julia> a = 1:3:20
1:3:19

julia> 4 in a
true

julia> 5 in a
false

julia> missing in [1, 2]
missing

julia> 1 in [2, missing]
missing

julia> 1 in [1, missing]
true

julia> missing in Set([1, 2])
false
source
Base.:∉Function.
∉(item, collection) -> Bool
∌(collection, item) -> Bool

Negation of and , i.e. checks that item is not in collection.

Examples

julia> 1 ∉ 2:4
true

julia> 1 ∉ 1:3
false
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Base.eltypeFunction.
eltype(type)

Determine the type of the elements generated by iterating a collection of the given type. For dictionary types, this will be a Pair{KeyType,ValType}. The definition eltype(x) = eltype(typeof(x)) is provided for convenience so that instances can be passed instead of types. However the form that accepts a type argument should be defined for new types.

Examples

julia> eltype(fill(1f0, (2,2)))
Float32

julia> eltype(fill(0x1, (2,2)))
UInt8
source
Base.indexinFunction.
indexin(a, b)

Return an array containing the first index in b for each value in a that is a member of b. The output array contains nothing wherever a is not a member of b.

Examples

julia> a = ['a', 'b', 'c', 'b', 'd', 'a'];

julia> b = ['a', 'b', 'c'];

julia> indexin(a, b)
6-element Array{Union{Nothing, Int64},1}:
1
2
3
2
nothing
1

julia> indexin(b, a)
3-element Array{Union{Nothing, Int64},1}:
1
2
3
source
Base.uniqueFunction.
unique(itr)

Return an array containing only the unique elements of collection itr, as determined by isequal, in the order that the first of each set of equivalent elements originally appears. The element type of the input is preserved.

Examples

julia> unique([1, 2, 6, 2])
3-element Array{Int64,1}:
1
2
6

julia> unique(Real[1, 1.0, 2])
2-element Array{Real,1}:
1
2
source
unique(f, itr)

Returns an array containing one value from itr for each unique value produced by f applied to elements of itr.

Examples

julia> unique(x -> x^2, [1, -1, 3, -3, 4])
3-element Array{Int64,1}:
1
3
4
source
unique(A::AbstractArray; dims::Int)

Return unique regions of A along dimension dims.

Examples

julia> A = map(isodd, reshape(Vector(1:8), (2,2,2)))
2×2×2 Array{Bool,3}:
[:, :, 1] =
true   true
false  false

[:, :, 2] =
true   true
false  false

julia> unique(A)
2-element Array{Bool,1}:
true
false

julia> unique(A, dims=2)
2×1×2 Array{Bool,3}:
[:, :, 1] =
true
false

[:, :, 2] =
true
false

julia> unique(A, dims=3)
2×2×1 Array{Bool,3}:
[:, :, 1] =
true   true
false  false
source
Base.unique!Function.
unique!(f, A::AbstractVector)

Selects one value from A for each unique value produced by f applied to elements of A , then return the modified A.

Julia 1.1

This method is available as of Julia 1.1.

Examples

julia> unique!(x -> x^2, [1, -1, 3, -3, 4])
3-element Array{Int64,1}:
1
3
4

julia> unique!(n -> n%3, [5, 1, 8, 9, 3, 4, 10, 7, 2, 6])
3-element Array{Int64,1}:
5
1
9

julia> unique!(iseven, [2, 3, 5, 7, 9])
2-element Array{Int64,1}:
2
3
source
unique!(A::AbstractVector)

Remove duplicate items as determined by isequal, then return the modified A. unique! will return the elements of A in the order that they occur. If you do not care about the order of the returned data, then calling (sort!(A); unique!(A)) will be much more efficient as long as the elements of A can be sorted.

Examples

julia> unique!([1, 1, 1])
1-element Array{Int64,1}:
1

julia> A = [7, 3, 2, 3, 7, 5];

julia> unique!(A)
4-element Array{Int64,1}:
7
3
2
5

julia> B = [7, 6, 42, 6, 7, 42];

julia> sort!(B);  # unique! is able to process sorted data much more efficiently.

julia> unique!(B)
3-element Array{Int64,1}:
6
7
42
source
Base.alluniqueFunction.
allunique(itr) -> Bool

Return true if all values from itr are distinct when compared with isequal.

Examples

julia> a = [1; 2; 3]
3-element Array{Int64,1}:
1
2
3

julia> allunique([a, a])
false
source
Base.reduceMethod.
reduce(op, itr; [init])

Reduce the given collection itr with the given binary operator op. If provided, the initial value init must be a neutral element for op that will be returned for empty collections. It is unspecified whether init is used for non-empty collections.

For empty collections, providing init will be necessary, except for some special cases (e.g. when op is one of +, *, max, min, &, |) when Julia can determine the neutral element of op.

Reductions for certain commonly-used operators may have special implementations, and should be used instead: maximum(itr), minimum(itr), sum(itr), prod(itr), any(itr), all(itr).

The associativity of the reduction is implementation dependent. This means that you can't use non-associative operations like - because it is undefined whether reduce(-,[1,2,3]) should be evaluated as (1-2)-3 or 1-(2-3). Use foldl or foldr instead for guaranteed left or right associativity.

Some operations accumulate error. Parallelism will be easier if the reduction can be executed in groups. Future versions of Julia might change the algorithm. Note that the elements are not reordered if you use an ordered collection.

Examples

julia> reduce(*, [2; 3; 4])
24

julia> reduce(*, [2; 3; 4]; init=-1)
-24
source
Base.foldlMethod.
foldl(op, itr; [init])

Like reduce, but with guaranteed left associativity. If provided, the keyword argument init will be used exactly once. In general, it will be necessary to provide init to work with empty collections.

Examples

julia> foldl(=>, 1:4)
((1=>2)=>3) => 4

julia> foldl(=>, 1:4; init=0)
(((0=>1)=>2)=>3) => 4
source
Base.foldrMethod.
foldr(op, itr; [init])

Like reduce, but with guaranteed right associativity. If provided, the keyword argument init will be used exactly once. In general, it will be necessary to provide init to work with empty collections.

Examples

julia> foldr(=>, 1:4)
1 => (2=>(3=>4))

julia> foldr(=>, 1:4; init=0)
1 => (2=>(3=>(4=>0)))
source
Base.maximumFunction.
maximum(itr)

Returns the largest element in a collection.

Examples

julia> maximum(-20.5:10)
9.5

julia> maximum([1,2,3])
3
source
maximum(A::AbstractArray; dims)

Compute the maximum value of an array over the given dimensions. See also the max(a,b) function to take the maximum of two or more arguments, which can be applied elementwise to arrays via max.(a,b).

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> maximum(A, dims=1)
1×2 Array{Int64,2}:
3  4

julia> maximum(A, dims=2)
2×1 Array{Int64,2}:
2
4
source
Base.maximum!Function.
maximum!(r, A)

Compute the maximum value of A over the singleton dimensions of r, and write results to r.

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> maximum!([1; 1], A)
2-element Array{Int64,1}:
2
4

julia> maximum!([1 1], A)
1×2 Array{Int64,2}:
3  4
source
Base.minimumFunction.
minimum(itr)

Returns the smallest element in a collection.

Examples

julia> minimum(-20.5:10)
-20.5

julia> minimum([1,2,3])
1
source
minimum(A::AbstractArray; dims)

Compute the minimum value of an array over the given dimensions. See also the min(a,b) function to take the minimum of two or more arguments, which can be applied elementwise to arrays via min.(a,b).

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> minimum(A, dims=1)
1×2 Array{Int64,2}:
1  2

julia> minimum(A, dims=2)
2×1 Array{Int64,2}:
1
3
source
Base.minimum!Function.
minimum!(r, A)

Compute the minimum value of A over the singleton dimensions of r, and write results to r.

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> minimum!([1; 1], A)
2-element Array{Int64,1}:
1
3

julia> minimum!([1 1], A)
1×2 Array{Int64,2}:
1  2
source
Base.extremaFunction.
extrema(itr) -> Tuple

Compute both the minimum and maximum element in a single pass, and return them as a 2-tuple.

Examples

julia> extrema(2:10)
(2, 10)

julia> extrema([9,pi,4.5])
(3.141592653589793, 9.0)
source
extrema(A::AbstractArray; dims) -> Array{Tuple}

Compute the minimum and maximum elements of an array over the given dimensions.

Examples

julia> A = reshape(Vector(1:2:16), (2,2,2))
2×2×2 Array{Int64,3}:
[:, :, 1] =
1  5
3  7

[:, :, 2] =
9  13
11  15

julia> extrema(A, dims = (1,2))
1×1×2 Array{Tuple{Int64,Int64},3}:
[:, :, 1] =
(1, 7)

[:, :, 2] =
(9, 15)
source
Base.argmaxFunction.
argmax(itr) -> Integer

Return the index of the maximum element in a collection. If there are multiple maximal elements, then the first one will be returned.

The collection must not be empty.

Examples

julia> argmax([8,0.1,-9,pi])
1

julia> argmax([1,7,7,6])
2

julia> argmax([1,7,7,NaN])
4
source
argmax(A; dims) -> indices

For an array input, return the indices of the maximum elements over the given dimensions. NaN is treated as greater than all other values.

Examples

julia> A = [1.0 2; 3 4]
2×2 Array{Float64,2}:
1.0  2.0
3.0  4.0

julia> argmax(A, dims=1)
1×2 Array{CartesianIndex{2},2}:
CartesianIndex(2, 1)  CartesianIndex(2, 2)

julia> argmax(A, dims=2)
2×1 Array{CartesianIndex{2},2}:
CartesianIndex(1, 2)
CartesianIndex(2, 2)
source
Base.argminFunction.
argmin(itr) -> Integer

Return the index of the minimum element in a collection. If there are multiple minimal elements, then the first one will be returned.

The collection must not be empty.

Examples

julia> argmin([8,0.1,-9,pi])
3

julia> argmin([7,1,1,6])
2

julia> argmin([7,1,1,NaN])
4
source
argmin(A; dims) -> indices

For an array input, return the indices of the minimum elements over the given dimensions. NaN is treated as less than all other values.

Examples

julia> A = [1.0 2; 3 4]
2×2 Array{Float64,2}:
1.0  2.0
3.0  4.0

julia> argmin(A, dims=1)
1×2 Array{CartesianIndex{2},2}:
CartesianIndex(1, 1)  CartesianIndex(1, 2)

julia> argmin(A, dims=2)
2×1 Array{CartesianIndex{2},2}:
CartesianIndex(1, 1)
CartesianIndex(2, 1)
source
Base.findmaxFunction.
findmax(itr) -> (x, index)

Return the maximum element of the collection itr and its index. If there are multiple maximal elements, then the first one will be returned. If any data element is NaN, this element is returned. The result is in line with max.

The collection must not be empty.

Examples

julia> findmax([8,0.1,-9,pi])
(8.0, 1)

julia> findmax([1,7,7,6])
(7, 2)

julia> findmax([1,7,7,NaN])
(NaN, 4)
source
findmax(A; dims) -> (maxval, index)

For an array input, returns the value and index of the maximum over the given dimensions. NaN is treated as greater than all other values.

Examples

julia> A = [1.0 2; 3 4]
2×2 Array{Float64,2}:
1.0  2.0
3.0  4.0

julia> findmax(A, dims=1)
([3.0 4.0], CartesianIndex{2}[CartesianIndex(2, 1) CartesianIndex(2, 2)])

julia> findmax(A, dims=2)
([2.0; 4.0], CartesianIndex{2}[CartesianIndex(1, 2); CartesianIndex(2, 2)])
source
Base.findminFunction.
findmin(itr) -> (x, index)

Return the minimum element of the collection itr and its index. If there are multiple minimal elements, then the first one will be returned. If any data element is NaN, this element is returned. The result is in line with min.

The collection must not be empty.

Examples

julia> findmin([8,0.1,-9,pi])
(-9.0, 3)

julia> findmin([7,1,1,6])
(1, 2)

julia> findmin([7,1,1,NaN])
(NaN, 4)
source
findmin(A; dims) -> (minval, index)

For an array input, returns the value and index of the minimum over the given dimensions. NaN is treated as less than all other values.

Examples

julia> A = [1.0 2; 3 4]
2×2 Array{Float64,2}:
1.0  2.0
3.0  4.0

julia> findmin(A, dims=1)
([1.0 2.0], CartesianIndex{2}[CartesianIndex(1, 1) CartesianIndex(1, 2)])

julia> findmin(A, dims=2)
([1.0; 3.0], CartesianIndex{2}[CartesianIndex(1, 1); CartesianIndex(2, 1)])
source
Base.findmax!Function.
findmax!(rval, rind, A) -> (maxval, index)

Find the maximum of A and the corresponding linear index along singleton dimensions of rval and rind, and store the results in rval and rind. NaN is treated as greater than all other values.

source
Base.findmin!Function.
findmin!(rval, rind, A) -> (minval, index)

Find the minimum of A and the corresponding linear index along singleton dimensions of rval and rind, and store the results in rval and rind. NaN is treated as less than all other values.

source
Base.sumFunction.
sum(f, itr)

Sum the results of calling function f on each element of itr.

The return type is Int for signed integers of less than system word size, and UInt for unsigned integers of less than system word size. For all other arguments, a common return type is found to which all arguments are promoted.

Examples

julia> sum(abs2, [2; 3; 4])
29

Note the important difference between sum(A) and reduce(+, A) for arrays with small integer eltype:

julia> sum(Int8[100, 28])
128

julia> reduce(+, Int8[100, 28])
-128

In the former case, the integers are widened to system word size and therefore the result is 128. In the latter case, no such widening happens and integer overflow results in -128.

source
sum(itr)

Returns the sum of all elements in a collection.

The return type is Int for signed integers of less than system word size, and UInt for unsigned integers of less than system word size. For all other arguments, a common return type is found to which all arguments are promoted.

Examples

julia> sum(1:20)
210
source
sum(A::AbstractArray; dims)

Sum elements of an array over the given dimensions.

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> sum(A, dims=1)
1×2 Array{Int64,2}:
4  6

julia> sum(A, dims=2)
2×1 Array{Int64,2}:
3
7
source
Base.sum!Function.
sum!(r, A)

Sum elements of A over the singleton dimensions of r, and write results to r.

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> sum!([1; 1], A)
2-element Array{Int64,1}:
3
7

julia> sum!([1 1], A)
1×2 Array{Int64,2}:
4  6
source
Base.prodFunction.
prod(f, itr)

Returns the product of f applied to each element of itr.

The return type is Int for signed integers of less than system word size, and UInt for unsigned integers of less than system word size. For all other arguments, a common return type is found to which all arguments are promoted.

Examples

julia> prod(abs2, [2; 3; 4])
576
source
prod(itr)

Returns the product of all elements of a collection.

The return type is Int for signed integers of less than system word size, and UInt for unsigned integers of less than system word size. For all other arguments, a common return type is found to which all arguments are promoted.

Examples

julia> prod(1:20)
2432902008176640000
source
prod(A::AbstractArray; dims)

Multiply elements of an array over the given dimensions.

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> prod(A, dims=1)
1×2 Array{Int64,2}:
3  8

julia> prod(A, dims=2)
2×1 Array{Int64,2}:
2
12
source
Base.prod!Function.
prod!(r, A)

Multiply elements of A over the singleton dimensions of r, and write results to r.

Examples

julia> A = [1 2; 3 4]
2×2 Array{Int64,2}:
1  2
3  4

julia> prod!([1; 1], A)
2-element Array{Int64,1}:
2
12

julia> prod!([1 1], A)
1×2 Array{Int64,2}:
3  8
source
Base.anyMethod.
any(itr) -> Bool

Test whether any elements of a boolean collection are true, returning true as soon as the first true value in itr is encountered (short-circuiting).

If the input contains missing values, return missing if all non-missing values are false (or equivalently, if the input contains no true value), following three-valued logic.

Examples

julia> a = [true,false,false,true]
4-element Array{Bool,1}:
true
false
false
true

julia> any(a)
true

julia> any((println(i); v) for (i, v) in enumerate(a))
1
true

julia> any([missing, true])
true

julia> any([false, missing])
missing
source
Base.anyMethod.
any(p, itr) -> Bool

Determine whether predicate p returns true for any elements of itr, returning true as soon as the first item in itr for which p returns true is encountered (short-circuiting).

If the input contains missing values, return missing if all non-missing values are false (or equivalently, if the input contains no true value), following three-valued logic.

Examples

julia> any(i->(4<=i<=6), [3,5,7])
true

julia> any(i -> (println(i); i > 3), 1:10)
1
2
3
4
true

julia> any(i -> i > 0, [1, missing])
true

julia> any(i -> i > 0, [-1, missing])
missing

julia> any(i -> i > 0, [-1, 0])
false
source
Base.any!Function.
any!(r, A)

Test whether any values in A along the singleton dimensions of r are true, and write results to r.

Examples

julia> A = [true false; true false]
2×2 Array{Bool,2}:
true  false
true  false

julia> any!([1; 1], A)
2-element Array{Int64,1}:
1
1

julia> any!([1 1], A)
1×2 Array{Int64,2}:
1  0
source
Base.allMethod.
all(itr) -> Bool

Test whether all elements of a boolean collection are true, returning false as soon as the first false value in itr is encountered (short-circuiting).

If the input contains missing values, return missing if all non-missing values are true (or equivalently, if the input contains no false value), following three-valued logic.

Examples

julia> a = [true,false,false,true]
4-element Array{Bool,1}:
true
false
false
true

julia> all(a)
false

julia> all((println(i); v) for (i, v) in enumerate(a))
1
2
false

julia> all([missing, false])
false

julia> all([true, missing])
missing
source
Base.allMethod.
all(p, itr) -> Bool

Determine whether predicate p returns true for all elements of itr, returning false as soon as the first item in itr for which p returns false is encountered (short-circuiting).

If the input contains missing values, return missing if all non-missing values are true (or equivalently, if the input contains no false value), following three-valued logic.

Examples

julia> all(i->(4<=i<=6), [4,5,6])
true

julia> all(i -> (println(i); i < 3), 1:10)
1
2
3
false

julia> all(i -> i > 0, [1, missing])
missing

julia> all(i -> i > 0, [-1, missing])
false

julia> all(i -> i > 0, [1, 2])
true
source
Base.all!Function.
all!(r, A)

Test whether all values in A along the singleton dimensions of r are true, and write results to r.

Examples

julia> A = [true false; true false]
2×2 Array{Bool,2}:
true  false
true  false

julia> all!([1; 1], A)
2-element Array{Int64,1}:
0
0

julia> all!([1 1], A)
1×2 Array{Int64,2}:
1  0
source
Base.countFunction.
count(p, itr) -> Integer
count(itr) -> Integer

Count the number of elements in itr for which predicate p returns true. If p is omitted, counts the number of true elements in itr (which should be a collection of boolean values).

Examples

julia> count(i->(4<=i<=6), [2,3,4,5,6])
3

julia> count([true, false, true, true])
3
source
Base.anyMethod.
any(p, itr) -> Bool

Determine whether predicate p returns true for any elements of itr, returning true as soon as the first item in itr for which p returns true is encountered (short-circuiting).

If the input contains missing values, return missing if all non-missing values are false (or equivalently, if the input contains no true value), following three-valued logic.

Examples

julia> any(i->(4<=i<=6), [3,5,7])
true

julia> any(i -> (println(i); i > 3), 1:10)
1
2
3
4
true

julia> any(i -> i > 0, [1, missing])
true

julia> any(i -> i > 0, [-1, missing])
missing

julia> any(i -> i > 0, [-1, 0])
false
source
Base.allMethod.
all(p, itr) -> Bool

Determine whether predicate p returns true for all elements of itr, returning false as soon as the first item in itr for which p returns false is encountered (short-circuiting).

If the input contains missing values, return missing if all non-missing values are true (or equivalently, if the input contains no false value), following three-valued logic.

Examples

julia> all(i->(4<=i<=6), [4,5,6])
true

julia> all(i -> (println(i); i < 3), 1:10)
1
2
3
false

julia> all(i -> i > 0, [1, missing])
missing

julia> all(i -> i > 0, [-1, missing])
false

julia> all(i -> i > 0, [1, 2])
true
source
Base.foreachFunction.
foreach(f, c...) -> Nothing

Call function f on each element of iterable c. For multiple iterable arguments, f is called elementwise. foreach should be used instead of map when the results of f are not needed, for example in foreach(println, array).

Examples

julia> a = 1:3:7;

julia> foreach(x -> println(x^2), a)
1
16
49
source
Base.mapFunction.
map(f, c...) -> collection

Transform collection c by applying f to each element. For multiple collection arguments, apply f elementwise.

Examples

julia> map(x -> x * 2, [1, 2, 3])
3-element Array{Int64,1}:
2
4
6

julia> map(+, [1, 2, 3], [10, 20, 30])
3-element Array{Int64,1}:
11
22
33
source
Base.map!Function.
map!(function, destination, collection...)

Like map, but stores the result in destination rather than a new collection. destination must be at least as large as the first collection.

Examples

julia> a = zeros(3);

julia> map!(x -> x * 2, a, [1, 2, 3]);

julia> a
3-element Array{Float64,1}:
2.0
4.0
6.0
source
Base.mapreduceMethod.
mapreduce(f, op, itr; [init])

Apply function f to each element in itr, and then reduce the result using the binary function op. If provided, init must be a neutral element for op that will be returned for empty collections. It is unspecified whether init is used for non-empty collections. In general, it will be necessary to provide init to work with empty collections.

mapreduce is functionally equivalent to calling reduce(op, map(f, itr); init=init), but will in general execute faster since no intermediate collection needs to be created. See documentation for reduce and map.

Examples

julia> mapreduce(x->x^2, +, [1:3;]) # == 1 + 4 + 9
14

The associativity of the reduction is implementation-dependent. Additionally, some implementations may reuse the return value of f for elements that appear multiple times in itr. Use mapfoldl or mapfoldr instead for guaranteed left or right associativity and invocation of f for every value.

source
Base.mapfoldlMethod.
mapfoldl(f, op, itr; [init])

Like mapreduce, but with guaranteed left associativity, as in foldl. If provided, the keyword argument init will be used exactly once. In general, it will be necessary to provide init to work with empty collections.

source
Base.mapfoldrMethod.
mapfoldr(f, op, itr; [init])

Like mapreduce, but with guaranteed right associativity, as in foldr. If provided, the keyword argument init will be used exactly once. In general, it will be necessary to provide init to work with empty collections.

source
Base.firstFunction.
first(coll)

Get the first element of an iterable collection. Return the start point of an AbstractRange even if it is empty.

Examples

julia> first(2:2:10)
2

julia> first([1; 2; 3; 4])
1
source
first(s::AbstractString, n::Integer)

Get a string consisting of the first n characters of s.

julia> first("∀ϵ≠0: ϵ²>0", 0)
""

julia> first("∀ϵ≠0: ϵ²>0", 1)
"∀"

julia> first("∀ϵ≠0: ϵ²>0", 3)
"∀ϵ≠"
source
Base.lastFunction.
last(coll)

Get the last element of an ordered collection, if it can be computed in O(1) time. This is accomplished by calling lastindex to get the last index. Return the end point of an AbstractRange even if it is empty.

Examples

julia> last(1:2:10)
9

julia> last([1; 2; 3; 4])
4
source
last(s::AbstractString, n::Integer)

Get a string consisting of the last n characters of s.

julia> last("∀ϵ≠0: ϵ²>0", 0)
""

julia> last("∀ϵ≠0: ϵ²>0", 1)
"0"

julia> last("∀ϵ≠0: ϵ²>0", 3)
"²>0"
source
Base.stepFunction.
step(r)

Get the step size of an AbstractRange object.

Examples

julia> step(1:10)
1

julia> step(1:2:10)
2

julia> step(2.5:0.3:10.9)
0.3

julia> step(range(2.5, stop=10.9, length=85))
0.1
source
Base.collectMethod.
collect(collection)

Return an Array of all items in a collection or iterator. For dictionaries, returns Pair{KeyType, ValType}. If the argument is array-like or is an iterator with the HasShape trait, the result will have the same shape and number of dimensions as the argument.

Examples

julia> collect(1:2:13)
7-element Array{Int64,1}:
1
3
5
7
9
11
13
source
Base.collectMethod.
collect(element_type, collection)

Return an Array with the given element type of all items in a collection or iterable. The result has the same shape and number of dimensions as collection.

Examples

julia> collect(Float64, 1:2:5)
3-element Array{Float64,1}:
1.0
3.0
5.0
source
Base.filterFunction.
filter(f, a::AbstractArray)

Return a copy of a, removing elements for which f is false. The function f is passed one argument.

Examples

julia> a = 1:10
1:10

julia> filter(isodd, a)
5-element Array{Int64,1}:
1
3
5
7
9
source
filter(f, d::AbstractDict)

Return a copy of d, removing elements for which f is false. The function f is passed key=>value pairs.

Examples

julia> d = Dict(1=>"a", 2=>"b")
Dict{Int64,String} with 2 entries:
2 => "b"
1 => "a"

julia> filter(p->isodd(p.first), d)
Dict{Int64,String} with 1 entry:
1 => "a"
source
Base.filter!Function.
filter!(f, a::AbstractVector)

Update a, removing elements for which f is false. The function f is passed one argument.

Examples

julia> filter!(isodd, Vector(1:10))
5-element Array{Int64,1}:
1
3
5
7
9
source
filter!(f, d::AbstractDict)

Update d, removing elements for which f is false. The function f is passed key=>value pairs.

Example

julia> d = Dict(1=>"a", 2=>"b", 3=>"c")
Dict{Int64,String} with 3 entries:
2 => "b"
3 => "c"
1 => "a"

julia> filter!(p->isodd(p.first), d)
Dict{Int64,String} with 2 entries:
3 => "c"
1 => "a"
source
Base.replaceMethod.
replace(A, old_new::Pair...; [count::Integer])

Return a copy of collection A where, for each pair old=>new in old_new, all occurrences of old are replaced by new. Equality is determined using isequal. If count is specified, then replace at most count occurrences in total.

The element type of the result is chosen using promotion (see promote_type) based on the element type of A and on the types of the new values in pairs. If count is omitted and the element type of A is a Union, the element type of the result will not include singleton types which are replaced with values of a different type: for example, Union{T,Missing} will become T if missing is replaced.

Examples

julia> replace([1, 2, 1, 3], 1=>0, 2=>4, count=2)
4-element Array{Int64,1}:
0
4
1
3

julia> replace([1, missing], missing=>0)
2-element Array{Int64,1}:
1
0
source
Base.replaceMethod.
replace(new::Function, A; [count::Integer])

Return a copy of A where each value x in A is replaced by new(x) If count is specified, then replace at most count values in total (replacements being defined as new(x) !== x).

Examples

julia> replace(x -> isodd(x) ? 2x : x, [1, 2, 3, 4])
4-element Array{Int64,1}:
2
2
6
4

julia> replace(Dict(1=>2, 3=>4)) do kv
first(kv) < 3 ? first(kv)=>3 : kv
end
Dict{Int64,Int64} with 2 entries:
3 => 4
1 => 3
source
Base.replace!Function.
replace!(A, old_new::Pair...; [count::Integer])

For each pair old=>new in old_new, replace all occurrences of old in collection A by new. Equality is determined using isequal. If count is specified, then replace at most count occurrences in total. See also replace.

Examples

julia> replace!([1, 2, 1, 3], 1=>0, 2=>4, count=2)
4-element Array{Int64,1}:
0
4
1
3

julia> replace!(Set([1, 2, 3]), 1=>0)
Set([0, 2, 3])
source
replace!(new::Function, A; [count::Integer])

Replace each element x in collection A by new(x). If count is specified, then replace at most count values in total (replacements being defined as new(x) !== x).

Examples

julia> replace!(x -> isodd(x) ? 2x : x, [1, 2, 3, 4])
4-element Array{Int64,1}:
2
2
6
4

julia> replace!(Dict(1=>2, 3=>4)) do kv
first(kv) < 3 ? first(kv)=>3 : kv
end
Dict{Int64,Int64} with 2 entries:
3 => 4
1 => 3

julia> replace!(x->2x, Set([3, 6]))
Set([6, 12])
source

## Indexable Collections

Base.getindexFunction.
getindex(collection, key...)

Retrieve the value(s) stored at the given key or index within a collection. The syntax a[i,j,...] is converted by the compiler to getindex(a, i, j, ...).

Examples

julia> A = Dict("a" => 1, "b" => 2)
Dict{String,Int64} with 2 entries:
"b" => 2
"a" => 1

julia> getindex(A, "a")
1
source
Base.setindex!Function.
setindex!(collection, value, key...)

Store the given value at the given key or index within a collection. The syntax a[i,j,...] = x is converted by the compiler to (setindex!(a, x, i, j, ...); x).

source
Base.firstindexFunction.
firstindex(collection) -> Integer
firstindex(collection, d) -> Integer

Return the first index of collection. If d is given, return the first index of collection along dimension d.

Examples

julia> firstindex([1,2,4])
1

julia> firstindex(rand(3,4,5), 2)
1
source
Base.lastindexFunction.
lastindex(collection) -> Integer
lastindex(collection, d) -> Integer

Return the last index of collection. If d is given, return the last index of collection along dimension d.

The syntaxes A[end] and A[end, end] lower to A[lastindex(A)] and A[lastindex(A, 1), lastindex(A, 2)], respectively.

Examples

julia> lastindex([1,2,4])
3

julia> lastindex(rand(3,4,5), 2)
4
source

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).

Base.DictType.
Dict([itr])

Dict{K,V}() constructs a hash table with keys of type K and values of type V. Keys are compared with isequal and hashed with hash.

Given a single iterable argument, constructs a Dict whose key-value pairs are taken from 2-tuples (key,value) generated by the argument.

Examples

julia> Dict([("A", 1), ("B", 2)])
Dict{String,Int64} with 2 entries:
"B" => 2
"A" => 1

Alternatively, a sequence of pair arguments may be passed.

julia> Dict("A"=>1, "B"=>2)
Dict{String,Int64} with 2 entries:
"B" => 2
"A" => 1
source
Base.IdDictType.
IdDict([itr])

IdDict{K,V}() constructs a hash table using object-id as hash and === as equality with keys of type K and values of type V.

See Dict for further help.

source
WeakKeyDict([itr])

WeakKeyDict() constructs a hash table where the keys are weak references to objects, and thus may be garbage collected even when referenced in a hash table.

See Dict for further help. Note, unlike Dict, WeakKeyDict does not convert keys on insertion.

source
ImmutableDict

ImmutableDict is a Dictionary implemented as an immutable linked list, which is optimal for small dictionaries that are constructed over many individual insertions Note that it is not possible to remove a value, although it can be partially overridden and hidden by inserting a new value with the same key

ImmutableDict(KV::Pair)

Create a new entry in the Immutable Dictionary for the key => value pair

• use (key => value) in dict to see if this particular combination is in the properties set
• use get(dict, key, default) to retrieve the most recent value for a particular key
source

Determine whether a collection has a mapping for a given key.

Examples

julia> D = Dict('a'=>2, 'b'=>3)
Dict{Char,Int64} with 2 entries:
'a' => 2
'b' => 3

true

false
source
Base.getMethod.
get(collection, key, default)

Return the value stored for the given key, or the given default value if no mapping for the key is present.

Examples

julia> d = Dict("a"=>1, "b"=>2);

julia> get(d, "a", 3)
1

julia> get(d, "c", 3)
3
source
Base.getFunction.
get(collection, key, default)

Return the value stored for the given key, or the given default value if no mapping for the key is present.

Examples

julia> d = Dict("a"=>1, "b"=>2);

julia> get(d, "a", 3)
1

julia> get(d, "c", 3)
3
source
get(f::Function, collection, key)

Return the value stored for the given key, or if no mapping for the key is present, return f(). Use get! to also store the default value in the dictionary.

This is intended to be called using do block syntax

get(dict, key) do
# default value calculated here
time()
end
source
Base.get!Method.
get!(collection, key, default)

Return the value stored for the given key, or if no mapping for the key is present, store key => default, and return default.

Examples

julia> d = Dict("a"=>1, "b"=>2, "c"=>3);

julia> get!(d, "a", 5)
1

julia> get!(d, "d", 4)
4

julia> d
Dict{String,Int64} with 4 entries:
"c" => 3
"b" => 2
"a" => 1
"d" => 4
source
Base.get!Method.
get!(f::Function, collection, key)

Return the value stored for the given key, or if no mapping for the key is present, store key => f(), and return f().

This is intended to be called using do block syntax:

get!(dict, key) do
# default value calculated here
time()
end
source
Base.getkeyFunction.
getkey(collection, key, default)

Return the key matching argument key if one exists in collection, otherwise return default.

Examples

julia> D = Dict('a'=>2, 'b'=>3)
Dict{Char,Int64} with 2 entries:
'a' => 2
'b' => 3

julia> getkey(D, 'a', 1)
'a': ASCII/Unicode U+0061 (category Ll: Letter, lowercase)

julia> getkey(D, 'd', 'a')
'a': ASCII/Unicode U+0061 (category Ll: Letter, lowercase)
source
Base.delete!Function.
delete!(collection, key)

Delete the mapping for the given key in a collection, and return the collection.

Examples

julia> d = Dict("a"=>1, "b"=>2)
Dict{String,Int64} with 2 entries:
"b" => 2
"a" => 1

julia> delete!(d, "b")
Dict{String,Int64} with 1 entry:
"a" => 1
source
Base.pop!Method.
pop!(collection, key[, default])

Delete and return the mapping for key if it exists in collection, otherwise return default, or throw an error if default is not specified.

Examples

julia> d = Dict("a"=>1, "b"=>2, "c"=>3);

julia> pop!(d, "a")
1

julia> pop!(d, "d")
Stacktrace:
[...]

julia> pop!(d, "e", 4)
4
source
Base.keysFunction.
keys(iterator)

For an iterator or collection that has keys and values (e.g. arrays and dictionaries), return an iterator over the keys.

source
Base.valuesFunction.
values(iterator)

For an iterator or collection that has keys and values, return an iterator over the values. This function simply returns its argument by default, since the elements of a general iterator are normally considered its "values".

Examples

julia> d = Dict("a"=>1, "b"=>2);

julia> values(d)
Base.ValueIterator for a Dict{String,Int64} with 2 entries. Values:
2
1

julia> values([2])
1-element Array{Int64,1}:
2
source
values(a::AbstractDict)

Return an iterator over all values in a collection. collect(values(a)) returns an array of values. Since the values are stored internally in a hash table, the order in which they are returned may vary. But keys(a) and values(a) both iterate a and return the elements in the same order.

Examples

julia> D = Dict('a'=>2, 'b'=>3)
Dict{Char,Int64} with 2 entries:
'a' => 2
'b' => 3

julia> collect(values(D))
2-element Array{Int64,1}:
2
3
source
Base.pairsFunction.
pairs(IndexLinear(), A)
pairs(IndexCartesian(), A)
pairs(IndexStyle(A), A)

An iterator that accesses each element of the array A, returning i => x, where i is the index for the element and x = A[i]. Identical to pairs(A), except that the style of index can be selected. Also similar to enumerate(A), except i will be a valid index for A, while enumerate always counts from 1 regardless of the indices of A.

Specifying IndexLinear() ensures that i will be an integer; specifying IndexCartesian() ensures that i will be a CartesianIndex; specifying IndexStyle(A) chooses whichever has been defined as the native indexing style for array A.

Mutation of the bounds of the underlying array will invalidate this iterator.

Examples

julia> A = ["a" "d"; "b" "e"; "c" "f"];

julia> for (index, value) in pairs(IndexStyle(A), A)
println("\$index \$value")
end
1 a
2 b
3 c
4 d
5 e
6 f

julia> S = view(A, 1:2, :);

julia> for (index, value) in pairs(IndexStyle(S), S)
println("\$index \$value")
end
CartesianIndex(1, 1) a
CartesianIndex(2, 1) b
CartesianIndex(1, 2) d
CartesianIndex(2, 2) e

source
pairs(collection)

Return an iterator over key => value pairs for any collection that maps a set of keys to a set of values. This includes arrays, where the keys are the array indices.

source
Base.mergeFunction.
merge(d::AbstractDict, others::AbstractDict...)

Construct a merged collection from the given collections. If necessary, the types of the resulting collection will be promoted to accommodate the types of the merged collections. If the same key is present in another collection, the value for that key will be the value it has in the last collection listed.

Examples

julia> a = Dict("foo" => 0.0, "bar" => 42.0)
Dict{String,Float64} with 2 entries:
"bar" => 42.0
"foo" => 0.0

julia> b = Dict("baz" => 17, "bar" => 4711)
Dict{String,Int64} with 2 entries:
"bar" => 4711
"baz" => 17

julia> merge(a, b)
Dict{String,Float64} with 3 entries:
"bar" => 4711.0
"baz" => 17.0
"foo" => 0.0

julia> merge(b, a)
Dict{String,Float64} with 3 entries:
"bar" => 42.0
"baz" => 17.0
"foo" => 0.0
source
merge(combine, d::AbstractDict, others::AbstractDict...)

Construct a merged collection from the given collections. If necessary, the types of the resulting collection will be promoted to accommodate the types of the merged collections. Values with the same key will be combined using the combiner function.

Examples

julia> a = Dict("foo" => 0.0, "bar" => 42.0)
Dict{String,Float64} with 2 entries:
"bar" => 42.0
"foo" => 0.0

julia> b = Dict("baz" => 17, "bar" => 4711)
Dict{String,Int64} with 2 entries:
"bar" => 4711
"baz" => 17

julia> merge(+, a, b)
Dict{String,Float64} with 3 entries:
"bar" => 4753.0
"baz" => 17.0
"foo" => 0.0
source
merge(a::NamedTuple, bs::NamedTuple...)

Construct a new named tuple by merging two or more existing ones, in a left-associative manner. Merging proceeds left-to-right, between pairs of named tuples, and so the order of fields present in both the leftmost and rightmost named tuples take the same position as they are found in the leftmost named tuple. However, values are taken from matching fields in the rightmost named tuple that contains that field. Fields present in only the rightmost named tuple of a pair are appended at the end. A fallback is implemented for when only a single named tuple is supplied, with signature merge(a::NamedTuple).

Julia 1.1

Merging 3 or more NamedTuple requires at least Julia 1.1.

Examples

julia> merge((a=1, b=2, c=3), (b=4, d=5))
(a = 1, b = 4, c = 3, d = 5)
julia> merge((a=1, b=2), (b=3, c=(d=1,)), (c=(d=2,),))
(a = 1, b = 3, c = (d = 2,))
source
merge(a::NamedTuple, iterable)

Interpret an iterable of key-value pairs as a named tuple, and perform a merge.

julia> merge((a=1, b=2, c=3), [:b=>4, :d=>5])
(a = 1, b = 4, c = 3, d = 5)
source
Base.merge!Method.
merge!(d::AbstractDict, others::AbstractDict...)

Examples

julia> d1 = Dict(1 => 2, 3 => 4);

julia> d2 = Dict(1 => 4, 4 => 5);

julia> merge!(d1, d2);

julia> d1
Dict{Int64,Int64} with 3 entries:
4 => 5
3 => 4
1 => 4
source
Base.merge!Method.
merge!(combine, d::AbstractDict, others::AbstractDict...)

Update collection with pairs from the other collections. Values with the same key will be combined using the combiner function.

Examples

julia> d1 = Dict(1 => 2, 3 => 4);

julia> d2 = Dict(1 => 4, 4 => 5);

julia> merge!(+, d1, d2);

julia> d1
Dict{Int64,Int64} with 3 entries:
4 => 5
3 => 4
1 => 6

julia> merge!(-, d1, d1);

julia> d1
Dict{Int64,Int64} with 3 entries:
4 => 0
3 => 0
1 => 0
source
Base.sizehint!Function.
sizehint!(s, n)

Suggest that collection s reserve capacity for at least n elements. This can improve performance.

source
Base.keytypeFunction.
keytype(type)

Get the key type of an dictionary type. Behaves similarly to eltype.

Examples

julia> keytype(Dict(Int32(1) => "foo"))
Int32
source
Base.valtypeFunction.
valtype(type)

Get the value type of an dictionary type. Behaves similarly to eltype.

Examples

julia> valtype(Dict(Int32(1) => "foo"))
String
source

Fully implemented by:

Partially implemented by:

## Set-Like Collections

Base.SetType.
Set([itr])

Construct a Set of the values generated by the given iterable object, or an empty set. Should be used instead of BitSet for sparse integer sets, or for sets of arbitrary objects.

source
Base.BitSetType.
BitSet([itr])

Construct a sorted set of Ints generated by the given iterable object, or an empty set. Implemented as a bit string, and therefore designed for dense integer sets. If the set will be sparse (for example, holding a few very large integers), use Set instead.

source
Base.unionFunction.
union(s, itrs...)
∪(s, itrs...)

Construct the union of sets. Maintain order with arrays.

Examples

julia> union([1, 2], [3, 4])
4-element Array{Int64,1}:
1
2
3
4

julia> union([1, 2], [2, 4])
3-element Array{Int64,1}:
1
2
4

julia> union([4, 2], 1:2)
3-element Array{Int64,1}:
4
2
1

julia> union(Set([1, 2]), 2:3)
Set([2, 3, 1])
source
Base.union!Function.
union!(s::Union{AbstractSet,AbstractVector}, itrs...)

Construct the union of passed in sets and overwrite s with the result. Maintain order with arrays.

Examples

julia> a = Set([1, 3, 4, 5]);

julia> union!(a, 1:2:8);

julia> a
Set([7, 4, 3, 5, 1])
source
Base.intersectFunction.
intersect(s, itrs...)
∩(s, itrs...)

Construct the intersection of sets. Maintain order with arrays.

Examples

julia> intersect([1, 2, 3], [3, 4, 5])
1-element Array{Int64,1}:
3

julia> intersect([1, 4, 4, 5, 6], [4, 6, 6, 7, 8])
2-element Array{Int64,1}:
4
6

julia> intersect(Set([1, 2]), BitSet([2, 3]))
Set([2])
source
Base.setdiffFunction.
setdiff(s, itrs...)

Construct the set of elements in s but not in any of the iterables in itrs. Maintain order with arrays.

Examples

julia> setdiff([1,2,3], [3,4,5])
2-element Array{Int64,1}:
1
2
source
Base.setdiff!Function.
setdiff!(s, itrs...)

Remove from set s (in-place) each element of each iterable from itrs. Maintain order with arrays.

Examples

julia> a = Set([1, 3, 4, 5]);

julia> setdiff!(a, 1:2:6);

julia> a
Set([4])
source
Base.symdiffFunction.
symdiff(s, itrs...)

Construct the symmetric difference of elements in the passed in sets. When s is not an AbstractSet, the order is maintained. Note that in this case the multiplicity of elements matters.

Examples

julia> symdiff([1,2,3], [3,4,5], [4,5,6])
3-element Array{Int64,1}:
1
2
6

julia> symdiff([1,2,1], [2, 1, 2])
2-element Array{Int64,1}:
1
2

julia> symdiff(unique([1,2,1]), unique([2, 1, 2]))
0-element Array{Int64,1}
source
Base.symdiff!Function.
symdiff!(s::Union{AbstractSet,AbstractVector}, itrs...)

Construct the symmetric difference of the passed in sets, and overwrite s with the result. When s is an array, the order is maintained. Note that in this case the multiplicity of elements matters.

source
Base.intersect!Function.
intersect!(s::Union{AbstractSet,AbstractVector}, itrs...)

Intersect all passed in sets and overwrite s with the result. Maintain order with arrays.

source
Base.issubsetFunction.
issubset(a, b)
⊆(a,b)  -> Bool
⊇(b, a) -> Bool

Determine whether every element of a is also in b, using in.

Examples

julia> issubset([1, 2], [1, 2, 3])
true

julia> [1, 2, 3] ⊆ [1, 2]
false

julia> [1, 2, 3] ⊇ [1, 2]
true
source
Base.:⊈Function.
⊈(a, b)
⊉(b, a)

Negation of and , i.e. checks that a is not a subset of b.

Examples

julia> (1, 2) ⊈ (2, 3)
true

julia> (1, 2) ⊈ (1, 2, 3)
false
source
Base.:⊊Function.
⊊(a, b)
⊋(b, a)

Determines if a is a subset of, but not equal to, b.

Examples

julia> (1, 2) ⊊ (1, 2, 3)
true

julia> (1, 2) ⊊ (1, 2)
false
source
Base.issetequalFunction.
issetequal(a, b)

Determine whether a and b have the same elements. Equivalent to a ⊆ b && b ⊆ a.

Examples

julia> issetequal([1, 2], [1, 2, 3])
false

julia> issetequal([1, 2], [2, 1])
true
source

Fully implemented by:

Partially implemented by:

## Dequeues

Base.push!Function.
push!(collection, items...) -> collection

Insert one or more items at the end of collection.

Examples

julia> push!([1, 2, 3], 4, 5, 6)
6-element Array{Int64,1}:
1
2
3
4
5
6

Use append! to add all the elements of another collection to collection. The result of the preceding example is equivalent to append!([1, 2, 3], [4, 5, 6]).

source
Base.pop!Function.
pop!(collection) -> item

Remove an item in collection and return it. If collection is an ordered container, the last item is returned.

Examples

julia> A=[1, 2, 3]
3-element Array{Int64,1}:
1
2
3

julia> pop!(A)
3

julia> A
2-element Array{Int64,1}:
1
2

julia> S = Set([1, 2])
Set([2, 1])

julia> pop!(S)
2

julia> S
Set([1])

julia> pop!(Dict(1=>2))
1 => 2
source
pop!(collection, key[, default])

Delete and return the mapping for key if it exists in collection, otherwise return default, or throw an error if default is not specified.

Examples

julia> d = Dict("a"=>1, "b"=>2, "c"=>3);

julia> pop!(d, "a")
1

julia> pop!(d, "d")
Stacktrace:
[...]

julia> pop!(d, "e", 4)
4
source
Base.pushfirst!Function.
pushfirst!(collection, items...) -> collection

Insert one or more items at the beginning of collection.

Examples

julia> pushfirst!([1, 2, 3, 4], 5, 6)
6-element Array{Int64,1}:
5
6
1
2
3
4
source
Base.popfirst!Function.
popfirst!(collection) -> item

Remove the first item from collection.

Examples

julia> A = [1, 2, 3, 4, 5, 6]
6-element Array{Int64,1}:
1
2
3
4
5
6

julia> popfirst!(A)
1

julia> A
5-element Array{Int64,1}:
2
3
4
5
6
source
Base.insert!Function.
insert!(a::Vector, index::Integer, item)

Insert an item into a at the given index. index is the index of item in the resulting a.

Examples

julia> insert!([6, 5, 4, 2, 1], 4, 3)
6-element Array{Int64,1}:
6
5
4
3
2
1
source
Base.deleteat!Function.
deleteat!(a::Vector, i::Integer)

Remove the item at the given i and return the modified a. Subsequent items are shifted to fill the resulting gap.

Examples

julia> deleteat!([6, 5, 4, 3, 2, 1], 2)
5-element Array{Int64,1}:
6
4
3
2
1
source
deleteat!(a::Vector, inds)

Remove the items at the indices given by inds, and return the modified a. Subsequent items are shifted to fill the resulting gap.

inds can be either an iterator or a collection of sorted and unique integer indices, or a boolean vector of the same length as a with true indicating entries to delete.

Examples

julia> deleteat!([6, 5, 4, 3, 2, 1], 1:2:5)
3-element Array{Int64,1}:
5
3
1

julia> deleteat!([6, 5, 4, 3, 2, 1], [true, false, true, false, true, false])
3-element Array{Int64,1}:
5
3
1

julia> deleteat!([6, 5, 4, 3, 2, 1], (2, 2))
ERROR: ArgumentError: indices must be unique and sorted
Stacktrace:
[...]
source
Base.splice!Function.
splice!(a::Vector, index::Integer, [replacement]) -> item

Remove the item at the given index, and return the removed item. Subsequent items are shifted left to fill the resulting gap. If specified, replacement values from an ordered collection will be spliced in place of the removed item.

Examples

julia> A = [6, 5, 4, 3, 2, 1]; splice!(A, 5)
2

julia> A
5-element Array{Int64,1}:
6
5
4
3
1

julia> splice!(A, 5, -1)
1

julia> A
5-element Array{Int64,1}:
6
5
4
3
-1

julia> splice!(A, 1, [-1, -2, -3])
6

julia> A
7-element Array{Int64,1}:
-1
-2
-3
5
4
3
-1

To insert replacement before an index n without removing any items, use splice!(collection, n:n-1, replacement).

source
splice!(a::Vector, range, [replacement]) -> items

Remove items in the specified index range, and return a collection containing the removed items. Subsequent items are shifted left to fill the resulting gap. If specified, replacement values from an ordered collection will be spliced in place of the removed items.

To insert replacement before an index n without removing any items, use splice!(collection, n:n-1, replacement).

Examples

julia> splice!(A, 4:3, 2)
0-element Array{Int64,1}

julia> A
8-element Array{Int64,1}:
-1
-2
-3
2
5
4
3
-1
source
Base.resize!Function.
resize!(a::Vector, n::Integer) -> Vector

Resize a to contain n elements. If n is smaller than the current collection length, the first n elements will be retained. If n is larger, the new elements are not guaranteed to be initialized.

Examples

julia> resize!([6, 5, 4, 3, 2, 1], 3)
3-element Array{Int64,1}:
6
5
4

julia> a = resize!([6, 5, 4, 3, 2, 1], 8);

julia> length(a)
8

julia> a[1:6]
6-element Array{Int64,1}:
6
5
4
3
2
1
source
Base.append!Function.
append!(collection, collection2) -> collection.

Add the elements of collection2 to the end of collection.

Examples

julia> append!([1],[2,3])
3-element Array{Int64,1}:
1
2
3

julia> append!([1, 2, 3], [4, 5, 6])
6-element Array{Int64,1}:
1
2
3
4
5
6

Use push! to add individual items to collection which are not already themselves in another collection. The result of the preceding example is equivalent to push!([1, 2, 3], 4, 5, 6).

source
Base.prepend!Function.
prepend!(a::Vector, items) -> collection

Insert the elements of items to the beginning of a.

Examples

julia> prepend!([3],[1,2])
3-element Array{Int64,1}:
1
2
3
source

Fully implemented by:

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

## Utility Collections

Base.PairType.
Pair(x, y)
x => y

Construct a Pair object with type Pair{typeof(x), typeof(y)}. The elements are stored in the fields first and second. They can also be accessed via iteration.

Examples

julia> p = "foo" => 7
"foo" => 7

julia> typeof(p)
Pair{String,Int64}

julia> p.first
"foo"

julia> for x in p
println(x)
end
foo
7
source
Iterators.Pairs(values, keys) <: AbstractDict{eltype(keys), eltype(values)}

Transforms an indexable container into an Dictionary-view of the same data. Modifying the key-space of the underlying data may invalidate this object.

source