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74 lines
2.5 KiB
ReStructuredText
74 lines
2.5 KiB
ReStructuredText
.. Copyright David Abrahams 2006. Distributed under the Boost
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.. Software License, Version 1.0. (See accompanying
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.. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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Example
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.......
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This example prints an array of characters, using
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``indirect_iterator`` to access the array of characters through an
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array of pointers. Next ``indirect_iterator`` is used with the
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``transform`` algorithm to copy the characters (incremented by one) to
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another array. A constant indirect iterator is used for the source and
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a mutable indirect iterator is used for the destination. The last part
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of the example prints the original array of characters, but this time
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using the ``make_indirect_iterator`` helper function.
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::
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char characters[] = "abcdefg";
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const int N = sizeof(characters)/sizeof(char) - 1; // -1 since characters has a null char
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char* pointers_to_chars[N]; // at the end.
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for (int i = 0; i < N; ++i)
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pointers_to_chars[i] = &characters[i];
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// Example of using indirect_iterator
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boost::indirect_iterator<char**, char>
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indirect_first(pointers_to_chars), indirect_last(pointers_to_chars + N);
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std::copy(indirect_first, indirect_last, std::ostream_iterator<char>(std::cout, ","));
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std::cout << std::endl;
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// Example of making mutable and constant indirect iterators
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char mutable_characters[N];
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char* pointers_to_mutable_chars[N];
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for (int j = 0; j < N; ++j)
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pointers_to_mutable_chars[j] = &mutable_characters[j];
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boost::indirect_iterator<char* const*> mutable_indirect_first(pointers_to_mutable_chars),
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mutable_indirect_last(pointers_to_mutable_chars + N);
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boost::indirect_iterator<char* const*, char const> const_indirect_first(pointers_to_chars),
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const_indirect_last(pointers_to_chars + N);
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std::transform(const_indirect_first, const_indirect_last,
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mutable_indirect_first, std::bind1st(std::plus<char>(), 1));
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std::copy(mutable_indirect_first, mutable_indirect_last,
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std::ostream_iterator<char>(std::cout, ","));
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std::cout << std::endl;
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// Example of using make_indirect_iterator()
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std::copy(boost::make_indirect_iterator(pointers_to_chars),
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boost::make_indirect_iterator(pointers_to_chars + N),
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std::ostream_iterator<char>(std::cout, ","));
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std::cout << std::endl;
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The output is::
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a,b,c,d,e,f,g,
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b,c,d,e,f,g,h,
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a,b,c,d,e,f,g,
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The source code for this example can be found `here`__.
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__ ../example/indirect_iterator_example.cpp
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