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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 | //# BinarySearch.h: Binary search through linear, sorted, data structures
//# Copyright (C) 1995,1996,1999
//# Associated Universities, Inc. Washington DC, USA.
//#
//# This library is free software; you can redistribute it and/or modify it
//# under the terms of the GNU Library General Public License as published by
//# the Free Software Foundation; either version 2 of the License, or (at your
//# option) any later version.
//#
//# This library is distributed in the hope that it will be useful, but WITHOUT
//# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
//# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
//# License for more details.
//#
//# You should have received a copy of the GNU Library General Public License
//# along with this library; if not, write to the Free Software Foundation,
//# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
//#
//# Correspondence concerning AIPS++ should be addressed as follows:
//# Internet email: aips2-request@nrao.edu.
//# Postal address: AIPS++ Project Office
//# National Radio Astronomy Observatory
//# 520 Edgemont Road
//# Charlottesville, VA 22903-2475 USA
//#
//#
//# $Id$
#ifndef CASA_BINARYSEARCH_H
#define CASA_BINARYSEARCH_H
//# Includes
#include <casacore/casa/aips.h>
namespace casacore { //# NAMESPACE CASACORE - BEGIN
// <summary>
// Binary search a sorted, linear, data structure.
// </summary>
// <reviewed reviewer="Ger van Diepen" date="1995/03/31" tests="tBinarySearch" demos="">
// </reviewed>
// <synopsis>
// These binary search functions work on sorted, linear data structures
// which have operator() or operator[] defined on them (<i>e.g.</i>
// C-array, Vector, IPosition, Block, ScalarColumn, <i>etc.</i>)
// Two versions of the functions are provided, one which uses
// parentheses () for indexing, one which uses square brackets [] (obviously
// the latter one can also be used for ordinary C-style pointers and arrays).
// It is assumed that the container uses zero-based indexing.
//
// The container must be sorted (sorting is available through the
// <linkto class="Sort">Sort</linkto> and
// <linkto class="GenSort">GenSort</linkto>
// classes, and from various
// <linkto class="Table">Table</linkto> sort functions). The returned index
// is in the range [0..n] inclusive. That is, from the first element of the
// container to one past the last element of the container (zero-based indices).
// If the container is sorted in ascending order, the returned index is the
// first one whose element is greater than or equal to the searched for value.
// If it is sorted in descending order, the returned index is the first which
// is less than or equal to the searched for value. That is, the returned
// index gives the position at which the value would be inserted (possibly
// either at the end, or requiring the existing values to be "pushed" to the
// right) maintaining the sort order. Obviously index n can only be
// returned if the value searched for is past the end of the array, thus
// has to be inserted at the end.
//
// The functions determine for themselves whether the container is sorted in
// ascending or descending order by comparing the first and last element.
// <note role=tip>
// While normally you want to search a container with indices in the range
// <src>[0 ... n-1]</src>, any desired lower bound may be used instead.
// </note>
// <note role=warning>
// The functions do not check if the container is valid, <i>i.e.</i> if
// the container is sorted and if the container does not contain duplicate
// values.
// </note>
//
// These functions loosely follow some written by Ger van Diepen in a more
// specialized context.
// </synopsis>
//
// <example>
// <srcblock>
// Vector<Int> vi;
// ... // Sets vi somehow
// genSort(vi);
// Int val;
// Bool found;
// while (cin >> val && val != -999) {
// Int where = binarySearch(found, vi, val, vi.nelements());
// if (found) {
// cout << "Found " << val << " at position " << where << endl;
// } else {
// cout << val << " is not in the vector, but it belongs at " <<
// where << endl;
// }
// }
// </srcblock>
// </example>
//
// <motivation>
// I found that I (BEG) was writing binary search functions several times,
// for example when checking whether the cached off and gain scans in time
// sorted data needed to be refilled. It generally seems like a useful little
// utility function.
// </motivation>
//
// <templating arg=Container>
// <li> operator(Int) or operator[Int] needs to be defined.
// <li> The index must be zero based.
// <li> The result of that indexing must be an expression that can be
// compared with an object of class ElType. Normally in fact it would
// be a temporary of class ElType.
// </templating>
// <templating arg=ElType>
// <li> The less than operator (<) and greater than (>) operators need to
// be defined, and have their usual ordering relations.
// </templating>
//
// <todo asof="yyyy/mm/dd">
// <li> I suspect that an implementation is possible that only calls
// operator() or [] once during each evaluation of the while loop.
// <li> MACROize implementation so that code isn't repeated twice. Or,
// possibly implement one using the other (e.g. by introducing an adapter
// class that turns (i) into [i].
// </todo>
// <group name=binarysearch>
// Search <i>container</i> for <i>value</i>. There are assumed to be at least
// <i>n</i> elements in the container. The container will be searched for
// indices in the range <src>[lower ... lower + n - 1]</src> Return the index
// of the first element which is greater than or equal to (ascending order) or
// less than or equal to (descending order) the value.
// <group>
// This version of the function is for containers that use () for indexing.
template<class Container, class ElType>
Int binarySearch(Bool &found, const Container &container,
const ElType &value, uInt n, Int lower=0);
// This version of the function is for containers that use [] for indexing.
template<class Container, class ElType>
Int binarySearchBrackets(Bool &found, const Container &container,
const ElType &value, uInt n, Int lower=0);
// </group>
// </group>
} //# NAMESPACE CASACORE - END
#ifndef CASACORE_NO_AUTO_TEMPLATES
#include <casacore/casa/Utilities/BinarySearch.tcc>
#endif //# CASACORE_NO_AUTO_TEMPLATES
#endif
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