line datatype

Probably the most succinct explanation would be to copy & paste from the 
terminal...

tjhart=> create table a_line( foo line );
CREATE
tjhart=> insert into a_line ( foo ) values( '(0,0), (1,1)' );
ERROR:  line not yet implemented
tjhart=> select version();                               version
--------------------------------------------------------------------- PostgreSQL 7.2.1 on powerpc-apple-darwin5.3,
compiledby GCC 2.95.2
 
(1 row)


The documentation (datatype-geometric.html) indicates both a 'line' type 
and an 'lseg' type in the summary table at the top of the page. The same 
code above using the type 'lseg' in place of 'line' works just fine.

Why can I create a table with a column of type 'line' if I can't insert 
into it?