Package dag
Package dag implements a language for expressing directed acyclic
graphs.
The general syntax of a rule is:
a, b < c, d;
which means c and d come after a and b in the partial order
(that is, there are edges from c and d to a and b),
but doesn't provide a relative order between a vs b or c vs d.
The rules can chain together, as in:
e < f, g < h;
which is equivalent to
e < f, g;
f, g < h;
Except for the special bottom element "NONE", each name
must appear exactly once on the right-hand side of any rule.
That rule serves as the definition of the allowed successor
for that name. The definition must appear before any uses
of the name on the left-hand side of a rule. (That is, the
rules themselves must be ordered according to the partial
order, for easier reading by people.)
Negative assertions double-check the partial order:
i !< j
means that it must NOT be the case that i < j.
Negative assertions may appear anywhere in the rules,
even before i and j have been defined.
Comments begin with #.
type Graph struct {
Nodes []string
}
func Parse(dag string) (*Graph, error)
Parse parses the DAG language and returns the transitive closure of
the described graph. In the returned graph, there is an edge from "b"
to "a" if b < a (or a > b) in the partial order.
func (g *Graph) AddEdge(from, to string)
func (g *Graph) DelEdge(from, to string)
func (*Graph) Edges
¶
func (g *Graph) Edges(from string) []string
func (g *Graph) HasEdge(from, to string) bool
func (*Graph) Topo
¶
func (g *Graph) Topo() []string
Topo returns a topological sort of g. This function is deterministic.
func (g *Graph) TransitiveReduction()
TransitiveReduction removes edges from g that are transitively
reachable. g must be transitively closed.
func (g *Graph) Transpose()
Transpose reverses all edges in g.