oracular (3) binarysearch.3bobcat.gz
NAME
FBB::binary_search - Extensions to the STL binary_search function template
SYNOPSIS
#include <bobcat/binarysearch>
DESCRIPTION
The FBB::binary_search function templates extend the STL binary_search function templates by returning an
iterator to the found element, instead of a bool value informing the caller whether or not the searched
for element is present in a provided iterator range.
The bool value returned by the STL binary_search function template is often not the kind of information
the caller of the function is interested in. Rather, the caller will often want to use binary_search in
the way find_if is used: returning an iterator to an element or returning the end-iterator if the element
was not found.
Whereas find_if does not require the elements in the iterator range to be sorted, and therefore uses a
linear search, binary_search benefits from the sorted nature of the elements using a binary search
algorithm requiring 2 log N iterations to locate the searched for element rather than (on average) N/2
iterations. The FBB::binary_search algorithm uses this binary searching process while at the same time
allowing it to be used like find_if.
Since the FBB::binary_search function templates use the same number and types of parameters as the
stl::binary_search function templates and because they are implemented using the stl::lower_bound
algorithms the FBB namespace must explicitly be specified when calling binary_search.
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the
namespace FBB.
INHERITS FROM
-
OVERLOADED FUNCTIONS
In the following description several template type parameters are used. They are:
o Iterator represents an iterator type;
o Type represents a value of the type to which Iterator points.
o Comparator represents a comparator function or class type object which was used to sort the
elements to which the Iterator range refer;
o Iterator binary_search(Iterator begin, Iterator end, Type const &value):
Using a binary search algorithm value is searched for in the range of elements referred to by the
provided iterator range. If the value is found an iterator pointing to this value is returned,
otherwise end is returned. The elements in the range must have been sorted by the Type’s operator<
function.
o Iterator binary_search(Iterator begin, Iterator end, Type const &value, Comparator comparator):
Using a binary search algorithm value is searched for in the range of elements referred to by the
provided iterator range. If the value is found an iterator pointing to this value is returned,
otherwise end is returned. The elements and the provided value are compared using
comparator(*iterator, value) calls, where *iterator refers to an object in the provided iterator
range. The elements in the range must have been sorted by the Comparator function or function
object.
The comparator function is called with two arguments. The first argument refers to an element in
the begin..end range, the second argument refers to value.
Usually the types of these arguments are identical, but they may differ. Assuming that Iterator
refers to elements of a type Data, then comparison operators bool operator<(Data const &lhs, Type
const &rhs) and bool operator<(Type const &rhs, Data const &lhs) must both be available.
EXAMPLES
#include <iostream>
#include <string>
#include "../binarysearch"
using namespace std;
string words[] =
{
"eight", // alphabetically sorted number-names
"five",
"four",
"nine",
"one",
"seven",
"six",
"ten",
"three",
"two"
};
bool compFun(string const &left, string const &right)
{
return left < right;
}
int main()
{
string *ret = FBB::binary_search(words, words + 10, "five");
if (ret != words + 10)
cout << "five is at offset " << (ret - words) << endl;
ret = FBB::binary_search(words, words + 10, "grandpa");
if (ret == words + 10)
cout << "grandpa is not the name of a number\n";
ret = FBB::binary_search(words, words + 10, "five",
[&](string const &element, string const &value)
{
return element < value;
}
);
if (ret != words + 10)
cout << "five is at offset " << (ret - words) << endl;
ret = FBB::binary_search(words, words + 10, "grandpa", compFun);
// or use: Comparator()
if (ret == words + 10)
cout << "grandpa is not the name of a number\n";
}
and an example showing the use of different types:
#include <iostream>
#include <string>
#include "../binarysearch"
using namespace std;
struct Words
{
string str;
int value;
};
bool operator<(Words const &word, string const &str)
{
return word.str < str;
}
bool operator<(string const &str, Words const &word)
{
return str < word.str;
}
Words words[] =
{
{ "eight", 0 }, // alphabetically sorted number-names
{ "five", 0 },
{ "four", 0 },
{ "nine", 0 },
{ "one", 0 },
{ "seven", 0 },
{ "six", 0 },
{ "ten", 0 },
{ "three", 0 },
{ "two", 0 }
};
int main()
{
auto ret = FBB::binary_search(words, words + 10, "five",
[&](Words const &element, string const &value)
{
return element < value;
}
);
cout << (ret != words + 10 ? "found it" : "not present") << ’\n’;
}
FILES
bobcat/binarysearch - defines the template functions
SEE ALSO
bobcat(7)
BUGS
None reported.
BOBCAT PROJECT FILES
o https://fbb-git.gitlab.io/bobcat/: gitlab project page;
o bobcat_6.06.01-x.dsc: detached signature;
o bobcat_6.06.01-x.tar.gz: source archive;
o bobcat_6.06.01-x_i386.changes: change log;
o libbobcat1_6.06.01-x_*.deb: debian package containing the libraries;
o libbobcat1-dev_6.06.01-x_*.deb: debian package containing the libraries, headers and manual pages;
BOBCAT
Bobcat is an acronym of `Brokken’s Own Base Classes And Templates’.
COPYRIGHT
This is free software, distributed under the terms of the GNU General Public License (GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).