concat strings but spaces

Moin,

I try to concat values from three fields in a function like this:

create or replace function
 fconcat_name(varchar, varchar, varchar) returns varchar as '
    declare
    ttl alias for $1;
    vnm alias for $2;
    nme alias for $3;
    begin
     return ttl || '' '' || vnm || '' '' || nme;
    end;
' language plpgsql;

That works but if one of the fields is empty there are to much
spaces in the result. Is there any alternative to a monster
if-then construct?

Many thanks
Matthias