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43th chunk of `doc/src/sgml/datatype.sgml`
e2272b61c1b69a3ccf4abbb2d12fe40d4551a86e6827b8c50000000100000fa0
 <replaceable>A</replaceable> and <replaceable>B</replaceable> are not both zero.  Values
     of type <type>line</type> are input and output in the following form:
<synopsis>
{ <replaceable>A</replaceable>, <replaceable>B</replaceable>, <replaceable>C</replaceable> }
</synopsis>

     Alternatively, any of the following forms can be used for input:

<synopsis>
[ ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) ]
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
    <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   ,   <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
</synopsis>

     where
     <literal>(<replaceable>x1</replaceable>,<replaceable>y1</replaceable>)</literal>
     and
     <literal>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</literal>
     are two different points on the line.
    </para>
   </sect2>

   <sect2 id="datatype-lseg">
    <title>Line Segments</title>

    <indexterm>
     <primary>lseg</primary>
    </indexterm>

    <indexterm>
     <primary>line segment</primary>
    </indexterm>

    <para>
     Line segments are represented by pairs of points that are the endpoints
     of the segment.  Values of type <type>lseg</type> are specified using any
     of the following syntaxes:

<synopsis>
[ ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) ]
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
    <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   ,   <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
</synopsis>

     where
     <literal>(<replaceable>x1</replaceable>,<replaceable>y1</replaceable>)</literal>
     and
     <literal>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</literal>
     are the end points of the line segment.
    </para>

    <para>
     Line segments are output using the first syntax.
    </para>
   </sect2>

   <sect2 id="datatype-geometric-boxes">
    <title>Boxes</title>

    <indexterm>
     <primary>box (data type)</primary>
    </indexterm>

    <indexterm>
     <primary>rectangle</primary>
    </indexterm>

    <para>
     Boxes are represented by pairs of points that are opposite
     corners of the box.
     Values of type <type>box</type> are specified using any of the following
     syntaxes:

<synopsis>
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
    <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   ,   <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
</synopsis>

     where
     <literal>(<replaceable>x1</replaceable>,<replaceable>y1</replaceable>)</literal>
     and
     <literal>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</literal>
     are any two opposite corners of the box.
    </para>

    <para>
     Boxes are output using the second syntax.
    </para>

    <para>
     Any two opposite corners can be supplied on input, but the values
     will be reordered as needed to store the
     upper right and lower left corners, in that order.
    </para>
   </sect2>

   <sect2 id="datatype-geometric-paths">
    <title>Paths</title>

    <indexterm>
     <primary>path (data type)</primary>
    </indexterm>
Title: Geometric Data Types: Lines, Line Segments, Boxes, and Paths
Summary
This section describes the representation and syntax of geometric data types in PostgreSQL, including lines, line segments, boxes, and paths. Lines are represented by linear equations and can be input and output in various forms. Line segments are defined by pairs of endpoints and can be specified using different syntaxes. Boxes are represented by pairs of opposite corners and can also be input and output in various forms. Paths are another geometric data type that can be used to store and query spatial data.