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href="https://github.com/JuliaLang/julia/blob/master/doc/src/stdlib/iterators.md"><span class="fa"></span> Edit on GitHub</a></nav><hr/><div id="topbar"><span>Iteration utilities</span><a class="fa fa-bars" href="#"></a></div></header><h1><a class="nav-anchor" id="Iteration-utilities-1" href="#Iteration-utilities-1">Iteration utilities</a></h1><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.zip" href="#Base.Iterators.zip"><code>Base.Iterators.zip</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">zip(iters...)</code></pre><p>For a set of iterable objects, returns an iterable of tuples, where the <code>i</code>th tuple contains the <code>i</code>th component of each input iterable.</p><p>Note that <a href="iterators.html#Base.Iterators.zip"><code>zip</code></a> is its own inverse: <code>collect(zip(zip(a...)...)) == collect(a)</code>.</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> a = 1:5
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1:5
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julia> b = ["e","d","b","c","a"]
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5-element Array{String,1}:
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"e"
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"d"
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"b"
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"c"
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"a"
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julia> c = zip(a,b)
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Base.Iterators.Zip2{UnitRange{Int64},Array{String,1}}(1:5, String["e", "d", "b", "c", "a"])
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julia> length(c)
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5
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julia> first(c)
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(1, "e")</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L201-L232">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.enumerate" href="#Base.Iterators.enumerate"><code>Base.Iterators.enumerate</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">enumerate(iter)</code></pre><p>An iterator that yields <code>(i, x)</code> where <code>i</code> is a counter starting at 1, and <code>x</code> is the <code>i</code>th value from the given iterator. It's useful when you need not only the values <code>x</code> over which you are iterating, but also the number of iterations so far. Note that <code>i</code> may not be valid for indexing <code>iter</code>; it's also possible that <code>x != iter[i]</code>, if <code>iter</code> has indices that do not start at 1. See the <code>enumerate(IndexLinear(), iter)</code> method if you want to ensure that <code>i</code> is an index.</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> a = ["a", "b", "c"];
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julia> for (index, value) in enumerate(a)
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println("$index $value")
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end
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1 a
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2 b
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3 c</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L35-L58">source</a><div><pre><code class="language-none">enumerate(IndexLinear(), A)
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enumerate(IndexCartesian(), A)
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enumerate(IndexStyle(A), A)</code></pre><p>An iterator that accesses each element of the array <code>A</code>, returning <code>(i, x)</code>, where <code>i</code> is the index for the element and <code>x = A[i]</code>. This is similar to <code>enumerate(A)</code>, except <code>i</code> will always be a valid index for <code>A</code>.</p><p>Specifying <code>IndexLinear()</code> ensures that <code>i</code> will be an integer; specifying <code>IndexCartesian()</code> ensures that <code>i</code> will be a <code>CartesianIndex</code>; specifying <code>IndexStyle(A)</code> chooses whichever has been defined as the native indexing style for array <code>A</code>.</p><p><strong>Examples</strong></p><pre><code class="language-julia-repl">julia> A = ["a" "d"; "b" "e"; "c" "f"];
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julia> for (index, value) in enumerate(IndexStyle(A), A)
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println("$index $value")
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end
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1 a
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2 b
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3 c
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4 d
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5 e
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6 f
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julia> S = view(A, 1:2, :);
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julia> for (index, value) in enumerate(IndexStyle(S), S)
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println("$index $value")
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end
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CartesianIndex{2}((1, 1)) a
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CartesianIndex{2}((2, 1)) b
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CartesianIndex{2}((1, 2)) d
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CartesianIndex{2}((2, 2)) e</code></pre><p>Note that <code>enumerate(A)</code> returns <code>i</code> as a <em>counter</em> (always starting at 1), whereas <code>enumerate(IndexLinear(), A)</code> returns <code>i</code> as an <em>index</em> (starting at the first linear index of <code>A</code>, which may or may not be 1).</p><p>See also: <a href="arrays.html#Base.IndexStyle"><code>IndexStyle</code></a>, <a href="arrays.html#Base.indices-Tuple{Any}"><code>indices</code></a>.</p></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L80-L127">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.rest" href="#Base.Iterators.rest"><code>Base.Iterators.rest</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">rest(iter, state)</code></pre><p>An iterator that yields the same elements as <code>iter</code>, but starting at the given <code>state</code>.</p></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L312-L316">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.countfrom" href="#Base.Iterators.countfrom"><code>Base.Iterators.countfrom</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">countfrom(start=1, step=1)</code></pre><p>An iterator that counts forever, starting at <code>start</code> and incrementing by <code>step</code>.</p></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L337-L341">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.take" href="#Base.Iterators.take"><code>Base.Iterators.take</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">take(iter, n)</code></pre><p>An iterator that generates at most the first <code>n</code> elements of <code>iter</code>.</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> a = 1:2:11
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1:2:11
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julia> collect(a)
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6-element Array{Int64,1}:
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1
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3
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5
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7
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9
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11
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julia> collect(Iterators.take(a,3))
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3-element Array{Int64,1}:
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1
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3
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5</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L361-L387">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.drop" href="#Base.Iterators.drop"><code>Base.Iterators.drop</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">drop(iter, n)</code></pre><p>An iterator that generates all but the first <code>n</code> elements of <code>iter</code>.</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> a = 1:2:11
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1:2:11
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julia> collect(a)
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6-element Array{Int64,1}:
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1
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3
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5
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7
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9
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11
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julia> collect(Iterators.drop(a,4))
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2-element Array{Int64,1}:
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9
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11</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L418-L443">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.cycle" href="#Base.Iterators.cycle"><code>Base.Iterators.cycle</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">cycle(iter)</code></pre><p>An iterator that cycles through <code>iter</code> forever.</p></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L477-L481">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.repeated" href="#Base.Iterators.repeated"><code>Base.Iterators.repeated</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">repeated(x[, n::Int])</code></pre><p>An iterator that generates the value <code>x</code> forever. If <code>n</code> is specified, generates <code>x</code> that many times (equivalent to <code>take(repeated(x), n)</code>).</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> a = Iterators.repeated([1 2], 4);
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julia> collect(a)
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4-element Array{Array{Int64,2},1}:
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[1 2]
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[1 2]
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[1 2]
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[1 2]</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L512-L530">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.product" href="#Base.Iterators.product"><code>Base.Iterators.product</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">product(iters...)</code></pre><p>Returns an iterator over the product of several iterators. Each generated element is a tuple whose <code>i</code>th element comes from the <code>i</code>th argument iterator. The first iterator changes the fastest. Example:</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> collect(Iterators.product(1:2,3:5))
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2×3 Array{Tuple{Int64,Int64},2}:
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(1, 3) (1, 4) (1, 5)
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(2, 3) (2, 4) (2, 5)</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L602-L617">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.flatten" href="#Base.Iterators.flatten"><code>Base.Iterators.flatten</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">flatten(iter)</code></pre><p>Given an iterator that yields iterators, return an iterator that yields the elements of those iterators. Put differently, the elements of the argument iterator are concatenated.</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> collect(Iterators.flatten((1:2, 8:9)))
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4-element Array{Int64,1}:
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1
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2
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8
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9</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L681-L698">source</a></section><section class="docstring"><div class="docstring-header"><a class="docstring-binding" id="Base.Iterators.partition" href="#Base.Iterators.partition"><code>Base.Iterators.partition</code></a> — <span class="docstring-category">Function</span>.</div><div><pre><code class="language-none">partition(collection, n)</code></pre><p>Iterate over a collection <code>n</code> elements at a time.</p><p><strong>Example</strong></p><pre><code class="language-julia-repl">julia> collect(Iterators.partition([1,2,3,4,5], 2))
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3-element Array{Array{Int64,1},1}:
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[1, 2]
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[3, 4]
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[5]</code></pre></div><a class="source-link" target="_blank" href="https://github.com/JuliaLang/julia/blob/d55cadc350d426a95fd967121ba77494d08364c8/base/iterators.jl#L738-L752">source</a></section><footer><hr/><a class="previous" href="dates.html"><span class="direction">Previous</span><span class="title">Dates and Time</span></a><a class="next" href="test.html"><span class="direction">Next</span><span class="title">Unit Testing</span></a></footer></article></body></html>
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