update comments

cmd/internal/graph/common.go

@@ -23,6 +23,8 @@ import (
 	"gonum.org/v1/gonum/mat"
 )
 
+// WeightedGraph is an interface so we can construct adjacency matrices for
+// both directed and undirected graphs.
 type WeightedGraph interface {
 	graph.Weighted
 	graph.WeightedMultigraph
@@ -31,6 +33,8 @@ type WeightedGraph interface {
 	WeightedEdges() graph.WeightedEdges
 }
 
+// WeightedMatrix is an interface to handle the construction of both directed
+// and undirected adjacency matrices.
 type WeightedMatrix interface {
 	graph.Weighted
 
@@ -65,6 +69,7 @@ func copyEdges(g WeightedGraph, adj WeightedMatrix) {
 	for edges := g.WeightedEdges(); edges.Next(); {
 		e := edges.WeightedEdge()
 		if e.From() == e.To() {
+			// the simple Matrix classes don't handle self loops
 			continue
 		}
 

cmd/internal/graph/dot/graph.go

@@ -25,7 +25,7 @@ import (
 	"gonum.org/v1/gonum/graph/multi"
 )
 
-// DOTWeightedGraph is a graph to unmarshal DOT graphs.
+// DOTWeightedGraph is a struct to unmarshal DOT graphs.
 type DOTWeightedGraph struct {
 	igraph.WeightedGraph
 	WeightAttribute string
@@ -36,6 +36,7 @@ func NewDOTDirectedGraph(weightAttr string) DOTWeightedGraph {
 	return DOTWeightedGraph{WeightedGraph: multi.NewWeightedDirectedGraph(), WeightAttribute: weightAttr}
 }
 
+// NewDOTUndirectedGraph returns a graph with no nodes or edges.
 func NewDOTUndirectedGraph(weightAttr string) DOTWeightedGraph {
 	return DOTWeightedGraph{WeightedGraph: multi.NewWeightedUndirectedGraph(), WeightAttribute: weightAttr}
 }

cmd/internal/graph/dot/nodes_edges.go

@@ -48,8 +48,8 @@ type weightedLine struct {
 	weightAttribute string
 }
 
-// SetAttribute enables storing the weight read from a DOT file. It errors if
-// an attribute is read that can't be stored in a weightedLine.
+// SetAttribute enables storing the weight read from a DOT file. It only errors
+// if the weight can't be parsed as a float.
 func (e *weightedLine) SetAttribute(attr encoding.Attribute) error {
 	var err error