378 lines
11 KiB
C++
378 lines
11 KiB
C++
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#ifndef DATE_TIME_PERIOD_HPP___
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#define DATE_TIME_PERIOD_HPP___
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/* Copyright (c) 2002,2003 CrystalClear Software, Inc.
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* Use, modification and distribution is subject to the
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* Boost Software License, Version 1.0. (See accompanying
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* file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
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* Author: Jeff Garland, Bart Garst
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* $Date$
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*/
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/*! \file period.hpp
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This file contain the implementation of the period abstraction. This is
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basically the same idea as a range. Although this class is intended for
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use in the time library, it is pretty close to general enough for other
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numeric uses.
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*/
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#include "boost/operators.hpp"
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namespace boost {
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namespace date_time {
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//!Provides generalized period type useful in date-time systems
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/*!This template uses a class to represent a time point within the period
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and another class to represent a duration. As a result, this class is
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not appropriate for use when the number and duration representation
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are the same (eg: in the regular number domain).
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A period can be specified by providing either the begining point and
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a duration or the begining point and the end point( end is NOT part
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of the period but 1 unit past it. A period will be "invalid" if either
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end_point <= begin_point or the given duration is <= 0. Any valid period
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will return false for is_null().
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Zero length periods are also considered invalid. Zero length periods are
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periods where the begining and end points are the same, or, the given
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duration is zero. For a zero length period, the last point will be one
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unit less than the begining point.
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In the case that the begin and last are the same, the period has a
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length of one unit.
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The best way to handle periods is usually to provide a begining point and
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a duration. So, day1 + 7 days is a week period which includes all of the
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first day and 6 more days (eg: Sun to Sat).
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*/
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template<class point_rep, class duration_rep>
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class period : private
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boost::less_than_comparable<period<point_rep, duration_rep>
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, boost::equality_comparable< period<point_rep, duration_rep>
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> >
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{
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public:
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typedef point_rep point_type;
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typedef duration_rep duration_type;
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period(point_rep first_point, point_rep end_point);
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period(point_rep first_point, duration_rep len);
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point_rep begin() const;
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point_rep end() const;
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point_rep last() const;
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duration_rep length() const;
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bool is_null() const;
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bool operator==(const period& rhs) const;
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bool operator<(const period& rhs) const;
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void shift(const duration_rep& d);
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void expand(const duration_rep& d);
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bool contains(const point_rep& point) const;
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bool contains(const period& other) const;
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bool intersects(const period& other) const;
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bool is_adjacent(const period& other) const;
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bool is_before(const point_rep& point) const;
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bool is_after(const point_rep& point) const;
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period intersection(const period& other) const;
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period merge(const period& other) const;
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period span(const period& other) const;
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private:
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point_rep begin_;
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point_rep last_;
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};
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//! create a period from begin to last eg: [begin,end)
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/*! If end <= begin then the period will be invalid
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*/
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template<class point_rep, class duration_rep>
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inline
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period<point_rep,duration_rep>::period(point_rep first_point,
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point_rep end_point) :
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begin_(first_point),
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last_(end_point - duration_rep::unit())
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{}
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//! create a period as [begin, begin+len)
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/*! If len is <= 0 then the period will be invalid
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*/
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template<class point_rep, class duration_rep>
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inline
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period<point_rep,duration_rep>::period(point_rep first_point, duration_rep len) :
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begin_(first_point),
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last_(first_point + len-duration_rep::unit())
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{ }
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//! Return the first element in the period
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template<class point_rep, class duration_rep>
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inline
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point_rep period<point_rep,duration_rep>::begin() const
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{
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return begin_;
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}
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//! Return one past the last element
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template<class point_rep, class duration_rep>
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inline
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point_rep period<point_rep,duration_rep>::end() const
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{
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return last_ + duration_rep::unit();
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}
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//! Return the last item in the period
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template<class point_rep, class duration_rep>
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inline
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point_rep period<point_rep,duration_rep>::last() const
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{
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return last_;
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}
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//! True if period is ill formed (length is zero or less)
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template<class point_rep, class duration_rep>
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inline
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bool period<point_rep,duration_rep>::is_null() const
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{
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return end() <= begin_;
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}
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//! Return the length of the period
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template<class point_rep, class duration_rep>
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inline
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duration_rep period<point_rep,duration_rep>::length() const
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{
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if(last_ < begin_){ // invalid period
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return last_+duration_rep::unit() - begin_;
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}
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else{
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return end() - begin_; // normal case
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}
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}
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//! Equality operator
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template<class point_rep, class duration_rep>
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inline
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bool period<point_rep,duration_rep>::operator==(const period& rhs) const
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{
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return ((begin_ == rhs.begin_) &&
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(last_ == rhs.last_));
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}
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//! Strict as defined by rhs.last <= lhs.last
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template<class point_rep, class duration_rep>
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inline
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bool period<point_rep,duration_rep>::operator<(const period& rhs) const
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{
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return (last_ < rhs.begin_);
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}
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//! Shift the start and end by the specified amount
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template<class point_rep, class duration_rep>
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inline
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void period<point_rep,duration_rep>::shift(const duration_rep& d)
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{
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begin_ = begin_ + d;
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last_ = last_ + d;
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}
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/** Expands the size of the period by the duration on both ends.
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*
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*So before expand
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*@code
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*
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* [-------]
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* ^ ^ ^ ^ ^ ^ ^
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* 1 2 3 4 5 6 7
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*
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*@endcode
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* After expand(2)
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*@code
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*
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* [----------------------]
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* ^ ^ ^ ^ ^ ^ ^
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* 1 2 3 4 5 6 7
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*
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*@endcode
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*/
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template<class point_rep, class duration_rep>
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inline
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void period<point_rep,duration_rep>::expand(const duration_rep& d)
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{
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begin_ = begin_ - d;
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last_ = last_ + d;
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}
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//! True if the point is inside the period, zero length periods contain no points
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template<class point_rep, class duration_rep>
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inline
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bool period<point_rep,duration_rep>::contains(const point_rep& point) const
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{
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return ((point >= begin_) &&
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(point <= last_));
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}
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//! True if this period fully contains (or equals) the other period
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template<class point_rep, class duration_rep>
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inline
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bool period<point_rep,duration_rep>::contains(const period<point_rep,duration_rep>& other) const
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{
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return ((begin_ <= other.begin_) && (last_ >= other.last_));
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}
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//! True if periods are next to each other without a gap.
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/* In the example below, p1 and p2 are adjacent, but p3 is not adjacent
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* with either of p1 or p2.
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*@code
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* [-p1-)
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* [-p2-)
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* [-p3-)
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*@endcode
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*/
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template<class point_rep, class duration_rep>
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inline
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bool
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period<point_rep,duration_rep>::is_adjacent(const period<point_rep,duration_rep>& other) const
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{
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return (other.begin() == end() ||
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begin_ == other.end());
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}
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//! True if all of the period is prior or t < start
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/* In the example below only point 1 would evaluate to true.
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*@code
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* [---------])
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* ^ ^ ^ ^ ^
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* 1 2 3 4 5
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*
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*@endcode
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*/
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template<class point_rep, class duration_rep>
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inline
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bool
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period<point_rep,duration_rep>::is_after(const point_rep& t) const
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{
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if (is_null())
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{
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return false; //null period isn't after
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}
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return t < begin_;
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}
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//! True if all of the period is prior to the passed point or end <= t
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/* In the example below points 4 and 5 return true.
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*@code
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* [---------])
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* ^ ^ ^ ^ ^
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* 1 2 3 4 5
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*
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*@endcode
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*/
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template<class point_rep, class duration_rep>
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inline
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bool
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period<point_rep,duration_rep>::is_before(const point_rep& t) const
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{
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if (is_null())
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{
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return false; //null period isn't before anything
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}
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return last_ < t;
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}
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//! True if the periods overlap in any way
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/* In the example below p1 intersects with p2, p4, and p6.
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*@code
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* [---p1---)
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* [---p2---)
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* [---p3---)
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* [---p4---)
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* [-p5-)
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* [-p6-)
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*@endcode
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*/
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template<class point_rep, class duration_rep>
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inline
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bool period<point_rep,duration_rep>::intersects(const period<point_rep,duration_rep>& other) const
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{
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return ( contains(other.begin_) ||
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other.contains(begin_) ||
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((other.begin_ < begin_) && (other.last_ >= begin_)));
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}
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//! Returns the period of intersection or invalid range no intersection
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template<class point_rep, class duration_rep>
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inline
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period<point_rep,duration_rep>
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period<point_rep,duration_rep>::intersection(const period<point_rep,duration_rep>& other) const
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{
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if (begin_ > other.begin_) {
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if (last_ <= other.last_) { //case2
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return *this;
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}
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//case 1
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return period<point_rep,duration_rep>(begin_, other.end());
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}
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else {
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if (last_ <= other.last_) { //case3
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return period<point_rep,duration_rep>(other.begin_, this->end());
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}
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//case4
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return other;
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}
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//unreachable
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}
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//! Returns the union of intersecting periods -- or null period
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/*!
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*/
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template<class point_rep, class duration_rep>
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inline
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period<point_rep,duration_rep>
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period<point_rep,duration_rep>::merge(const period<point_rep,duration_rep>& other) const
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{
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if (this->intersects(other)) {
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if (begin_ < other.begin_) {
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return period<point_rep,duration_rep>(begin_, last_ > other.last_ ? this->end() : other.end());
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}
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return period<point_rep,duration_rep>(other.begin_, last_ > other.last_ ? this->end() : other.end());
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}
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return period<point_rep,duration_rep>(begin_,begin_); // no intersect return null
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}
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//! Combine two periods with earliest start and latest end.
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/*! Combines two periods and any gap between them such that
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* start = min(p1.start, p2.start)
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* end = max(p1.end , p2.end)
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*@code
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* [---p1---)
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* [---p2---)
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* result:
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* [-----------p3----------)
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*@endcode
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*/
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template<class point_rep, class duration_rep>
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inline
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period<point_rep,duration_rep>
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period<point_rep,duration_rep>::span(const period<point_rep,duration_rep>& other) const
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{
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point_rep start((begin_ < other.begin_) ? begin() : other.begin());
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point_rep newend((last_ < other.last_) ? other.end() : this->end());
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return period<point_rep,duration_rep>(start, newend);
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}
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} } //namespace date_time
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#endif
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