# [tsp_getdistance]

 Link tsp_getdistance Author Jason Huck Category Math Version 8.x License http://opensource.org/licenses/artistic-license.php Posted 22 Jan 2006 Updated 22 Jan 2006 More by this author...

#### Description

This tag calculates the distance in miles, "as the crow flies", between two sets of coordinates. Used in combination with [tsp_getcosts] and [tsp_gettour], can be used to generate a "next-closest tour" to solve basic TSP problems.

#### Sample Usage

```// test data
var('cities') = array(
'Location A' = array(-82.521102,37.484227),
'Location B' = array(-84.622564,37.059857),
'Location C' = array(-84.622668,37.059893),
'Location D' = array(-82.642757,38.480449),
'Location E' = array(-84.600683,37.031884),
'Location F' = array(-85.062656,36.982708),
'Location G' = array(-84.623724,37.055167),
'Location H' = array(-84.622564,37.059857),
'Location I' = array(-84.072400,37.107600),
'Location J' = array(-84.335426,36.841322)
);

// distance example
'Distance between ' + \$cities->get(1)->first + ' and ' + \$cities->get(10)->first + ': ';

tsp_getdistance(
-startLat=\$cities->get(1)->second->get(2),
-startLong=\$cities->get(1)->second->get(1),
-endLat=\$cities->get(10)->second->get(2),
-endLong=\$cities->get(10)->second->get(1),
);

' miles\n';
```

#### Source Code

Click the "Download" button below to retrieve a copy of this tag, including the complete documentation and sample usage shown on this page. Place the downloaded ".inc" file in your LassoStartup folder, restart Lasso, and you can begin using this tag immediately.

```define_tag(
'getdistance',
-namespace='tsp_',
-priority='replace',
-required='startLat',
-type='decimal',
-required='startLong',
-type='decimal',
-required='endLat',
-type='decimal',
-required='endLong',
-type='decimal',
-description='Calculates distance in miles between two sets of coordinates.'
);
local('out') = math_sqrt(
69.1 * (
#endLat - #startLat
) * 69.1 * (
#endLat - #startLat
) + 53 * (
#endLong - #startLong
) * 53 * (
#endLong - #startLong
)
);

return(#out);
/define_tag;
```

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