（五） Graphivz 箭头连接方向

Ports based on the 8 compass points "n", "ne","e", "se", "s", "sw", "w" or "nw" can be specified for any node.

有八种连接方向：n，ne，e，se，s，sw，w，nw。

digraph G {
a->b:n[label="n"];
c->d:e[label="e"];
e->f:ne[label="ne"];
g->h:s[label="s"];
i->j:se[label="se"];
k->l:w[label="w"];
m->n:sw[label="sw"];
p->q:nw[label="nw"];
A -> B[dir = both,label=both];
B -> C[dir = none,label=none];
C -> D[dir = back,label=back];
D -> A[dir = forward,label=forward];
}