static object _Read(GridNode node)
{
var groups = node.Head
.Select((v, y) => (y: y + 1, v))
.Where(t => t.v != "")
.GroupBy(t => t.v)
.Select(g => SimpleGroup.From(g.Select(t => t.y), Sym.From(g.Key)))
.ToArray();
var map = groups.Aggregate(
Map <int, Sym> .Empty,
(m, g) => m.Add(GroupMap.Lift(g.Nodes, g.Value)));
if (node.Tail != null)
{
var right = Read(node.Tail).As <Map <int, Sym> >();
map = map.Add(right);
}
return(map);
}
public static SimpleGroup <int, Sym> Simple(this Group <int, Sym> group) => SimpleGroup.From(group.Nodes, group.Value);