Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

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length

Calculates the length of a geometry.

Description

The free function length calculates the length (the sum of distances between consecutive points) of a geometry. It uses the default strategy, based on the coordinate system of the geometry.

Synopsis

template<typename Geometry>
dispatch::devarianted_length<Geometry>::result_type length(Geometry const & geometry)

Parameters

Type

Concept

Name

Description

Geometry const &

Any type fulfilling a Geometry Concept

geometry

A model of the specified concept

Returns

The calculated length

Header

Either

#include <boost/geometry/geometry.hpp>

Or

#include <boost/geometry/algorithms/length.hpp>

Conformance

The function length implements function Length from the OGC Simple Feature Specification.

Behavior

Case

Behavior

pointlike (e.g. point)

Returns 0

linear (e.g. linestring)

Returns the length

areal (e.g. polygon)

Returns 0

Complexity

Linear

Examples

The following simple example shows the calculation of the length of a linestring containing three points

#include <iostream>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/linestring.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>


int main()
{
    using namespace boost::geometry;
    model::linestring<model::d2::point_xy<double> > line;
    read_wkt("linestring(0 0,1 1,4 8,3 2)", line);
    std::cout << "linestring length is "
        << length(line)
        << " units" << std::endl;

    return 0;
}

Output:

linestring length is 15.1127 units

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