Обсуждение: point(lseg,lseg) does not exist

Hi,

I am attempting a query using lseg values to find the point
of intersection.  The following query taken from the PG
manual isn't working over here.

select
point(lseg '((-1,0),(1,0))', lseg
'((-2,-2),(2,2))')
ERROR:  function point(lseg, lseg) does not exist
HINT:  No function matches the given name and argument
types. You may need to add explicit type casts.

Do I need to declare this function somewhere?  Pg version
7.4.7 (debian rev 6 Sarge).

Best regards,
Shane

--
Shane Wegner
http://www.cm.nu/~shane/

Shane <shane-pgsql@cm.nu> writes:
> I am attempting a query using lseg values to find the point
> of intersection.  The following query taken from the PG
> manual isn't working over here.

> select
> point(lseg '((-1,0),(1,0))', lseg
> '((-2,-2),(2,2))')
> ERROR:  function point(lseg, lseg) does not exist

Hm, seems to be a thinko in the documentation.  The function you
actually want is lseg_interpt(), which would probably be better
invoked via the documented operator lseg # lseg.

            regards, tom lane

Shane wrote:

>Hi,
>
>I am attempting a query using lseg values to find the point
>of intersection.  The following query taken from the PG
>manual isn't working over here.
>
>select
>point(lseg '((-1,0),(1,0))', lseg
>'((-2,-2),(2,2))')
>ERROR:  function point(lseg, lseg) does not exist
>HINT:  No function matches the given name and argument
>types. You may need to add explicit type casts.
>
>Do I need to declare this function somewhere?  Pg version
>7.4.7 (debian rev 6 Sarge).
>
>Best regards,
>Shane
>
>
>

Shane,

The operator for determining the intersection of two lsegs is #; thus,

select lseg # lseg

and the result is the intersection point.

Don