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