# give a name to a directory

$1=~+
: ~$1

# for example, if we say: namedir foo
# where the current directory is /usr/princeton/common/src/news/nntp/inews
# this will do:
#
# foo=/usr/princeton/common/src/news/nntp/inews
# : ~foo
#
# The : ~foo just evaluates ~foo, which declares foo as a named directory.
# The first time a parameter is used with tilde expansion, it is declared
# as the name of a named dir.