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pgraph: Don't panic on new or nil graphs

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This adds a bit of flexibility so that we can still run a topological
sort on a nil graph.
This commit is contained in:
James Shubin
2018-03-05 01:58:43 -05:00
parent a5c3db6303
commit 173ccf6861
1 changed files with 9 additions and 2 deletions
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11
pgraph/pgraph.go
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@@ -58,7 +58,9 @@ func (g *Graph) Init() error {
return fmt.Errorf("can't initialize graph with empty name") return fmt.Errorf("can't initialize graph with empty name")
} }
//g.adjacency = make(map[Vertex]map[Vertex]Edge) // not required if g.adjacency == nil {
g.adjacency = make(map[Vertex]map[Vertex]Edge)
}
//g.kv = make(map[string]interface{}) // not required //g.kv = make(map[string]interface{}) // not required
return nil return nil
} }
@@ -427,6 +429,9 @@ func (g *Graph) DisconnectedGraphs() ([]*Graph, error) {
// InDegree returns the count of vertices that point to me in one big lookup map. // InDegree returns the count of vertices that point to me in one big lookup map.
func (g *Graph) InDegree() map[Vertex]int { func (g *Graph) InDegree() map[Vertex]int {
result := make(map[Vertex]int) result := make(map[Vertex]int)
if g == nil || g.adjacency == nil {
return result
}
for k := range g.adjacency { for k := range g.adjacency {
result[k] = 0 // initialize result[k] = 0 // initialize
} }
@@ -442,7 +447,9 @@ func (g *Graph) InDegree() map[Vertex]int {
// OutDegree returns the count of vertices that point away in one big lookup map. // OutDegree returns the count of vertices that point away in one big lookup map.
func (g *Graph) OutDegree() map[Vertex]int { func (g *Graph) OutDegree() map[Vertex]int {
result := make(map[Vertex]int) result := make(map[Vertex]int)
if g == nil || g.adjacency == nil {
return result
}
for k := range g.adjacency { for k := range g.adjacency {
result[k] = 0 // initialize result[k] = 0 // initialize
for range g.adjacency[k] { for range g.adjacency[k] {