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#### Overview <a id="range.common.overview">[[range.common.overview]]</a>
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`common_view` takes a `view` which has different types for its iterator
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and sentinel and turns it into a `view` of the same elements with an
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iterator and sentinel of the same type.
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[*Note 1*: `common_view` is useful for calling legacy algorithms that
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expect a range’s iterator and sentinel types to be the
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same. — *end note*]
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The name `views::common` denotes a range adaptor object
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[[range.adaptor.object]]. Given a subexpression `E`, the expression
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`views::common(E)` is expression-equivalent to:
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- `views::all(E)`, if `decltype((E))` models `common_range` and
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`views::all(E)` is a well-formed expression.
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- Otherwise, `common_view{E}`.
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[*Example 1*:
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``` cpp
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// Legacy algorithm:
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template<class ForwardIterator>
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size_t count(ForwardIterator first, ForwardIterator last);
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template<forward_range R>
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void my_algo(R&& r) {
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auto&& common = common_view{r};
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auto cnt = count(common.begin(), common.end());
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// ...
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}
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```
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— *end example*]
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