70 lines
1.9 KiB
C++
70 lines
1.9 KiB
C++
// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
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#if !defined(CPPLINQ_LINQ_WHERE_HPP)
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#define CPPLINQ_LINQ_WHERE_HPP
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#pragma once
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namespace cpplinq
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{
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template <class Collection, class Predicate>
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class linq_where
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{
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typedef typename Collection::cursor
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inner_cursor;
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public:
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struct cursor {
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typedef typename util::min_iterator_category<
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bidirectional_cursor_tag,
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typename inner_cursor::cursor_category>::type
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cursor_category;
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typedef typename inner_cursor::element_type
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element_type;
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typedef typename inner_cursor::reference_type
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reference_type;
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cursor(const inner_cursor& cur, const Predicate& p) : cur(cur), pred(p)
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{
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if (!cur.empty() && !pred(cur.get())) {
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this->inc();
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}
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}
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void forget() { cur.forget(); }
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bool empty() const { return cur.empty(); }
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void inc() {
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for (;;) {
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cur.inc();
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if (cur.empty() || pred(cur.get())) break;
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}
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}
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reference_type get() const {
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return cur.get();
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}
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bool atbegin() const { return atbegin(cur); }
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void dec() {
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for (;;) {
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cur.dec();
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if (pred(cur.get())) break;
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}
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}
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private:
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inner_cursor cur;
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Predicate pred;
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};
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linq_where(const Collection& c, Predicate pred) : c(c), pred(pred) {}
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cursor get_cursor() const {
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return cursor(c.get_cursor(), pred);
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}
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private:
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Collection c;
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Predicate pred;
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};
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}
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#endif // !defined(CPPLINQ_LINQ_WHERE_HPP)
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