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84 lines
2.6 KiB
Plaintext
84 lines
2.6 KiB
Plaintext
[/ File find_not.qbk]
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[section:find_not find_not ]
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[/license
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Copyright (c) 2018 T. Zachary Laine
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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]
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The header file 'find_not.hpp' contains a variants of a the stl algorithm
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`find`. The algorithm finds the first value in the given sequence that is not
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equal to the given value.
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Consider this use of `find()`:
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std::vector<int> vec = { 1, 1, 2 };
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auto it = std::find(vec.begin(), vec.end(), 1);
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This gives us the first occurance of `1` in `vec`. What if we want to find
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the first occurrance of any number besides `1` in `vec`? We have to write an
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unfortunate amount of code:
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std::vector<int> vec = { 1, 1, 2 };
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auto it = std::find_if(vec.begin(), vec.end(), [](int i) { return i != 1; });
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With `find_not()` the code gets much more terse:
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std::vector<int> vec = { 1, 1, 2 };
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auto it = find_not(vec.begin(), vec.end(), 1);
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The existing `find` variants are: `find()`, `find_if()`, and `find_if_not()`.
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It seems natural to also have `find_not()`, for the very reason that we have
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`find_if_not()` -- to avoid having to write a lambda to wrap the negation of
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the find condition.
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[heading interface]
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template<typename InputIter, typename Sentinel, typename T>
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InputIter find_not(InputIter first, Sentinel last, const T & x);
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template<typename Range, typename T>
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boost::range_iterator<Range> find_not(Range & r, const T & x);
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These overloads of `find_not` return the first value that is not equal to `x`
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in the sequence `[first, last)` or `r`, respectively.
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[heading Examples]
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Given the container `c1` containing `{ 0, 1, 2 }`, then
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find_not ( c1.begin(), c1.end(), 1 ) --> c1.begin()
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find_not ( c1.begin(), c1.end(), 0 ) --> std::next(c1.begin())
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[heading Iterator Requirements]
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`find_not` works on all iterators except output iterators.
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The template parameter `Sentinel` is allowed to be different from `InputIter`,
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or they may be the same. For an `InputIter` `it` and a `Sentinel` `end`, `it
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== end` and `it != end` must be well-formed expressions.
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[heading Complexity]
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Linear.
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[heading Exception Safety]
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`find_not` takes its parameters by value and do not depend upon any global
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state. Therefore, it provides the strong exception guarantee.
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[heading Notes]
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`constexpr` in C++14 or later.
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[endsect]
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[/ File equal.qbk
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Copyright 2018 T. Zachary Laine
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt).
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]
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