1 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information. 2 3 #if !defined(CPPLINQ_LINQ_WHERE_HPP) 4 #define CPPLINQ_LINQ_WHERE_HPP 5 #pragma once 6 7 namespace cpplinq 8 { 9 template <class Collection, class Predicate> 10 class linq_where 11 { 12 typedef typename Collection::cursor 13 inner_cursor; 14 public: 15 struct cursor { 16 typedef typename util::min_iterator_category< 17 bidirectional_cursor_tag, 18 typename inner_cursor::cursor_category>::type 19 cursor_category; 20 typedef typename inner_cursor::element_type 21 element_type; 22 typedef typename inner_cursor::reference_type 23 reference_type; 24 25 cursor(const inner_cursor& cur, const Predicate& p) : cur(cur), pred(p) 26 { 27 if (!cur.empty() && !pred(cur.get())) { 28 this->inc(); 29 } 30 } 31 32 void forget() { cur.forget(); } 33 bool empty() const { return cur.empty(); } 34 void inc() { 35 for (;;) { 36 cur.inc(); 37 if (cur.empty() || pred(cur.get())) break; 38 } 39 } 40 reference_type get() const { 41 return cur.get(); 42 } 43 44 bool atbegin() const { return atbegin(cur); } 45 void dec() { 46 for (;;) { 47 cur.dec(); 48 if (pred(cur.get())) break; 49 } 50 } 51 private: 52 inner_cursor cur; 53 Predicate pred; 54 }; 55 56 linq_where(const Collection& c, Predicate pred) : c(c), pred(pred) {} 57 58 cursor get_cursor() const { 59 return cursor(c.get_cursor(), pred); 60 } 61 62 private: 63 Collection c; 64 Predicate pred; 65 }; 66 } 67 68 #endif // !defined(CPPLINQ_LINQ_WHERE_HPP) 69 70
