/** Create structure with stemma data, read from dot string **/
procedure readStemma(stemmastring) {
  local stemma = newstructure(V,"stemma")
  local pipe = assert(io.popen("echo '"..stemmastring.."' | dot -Tplain"))
  local s = pipe:read("*all")
  pipe:close()
-- Add nodes to the stemma.
  local t = {}
  for node in string.gmatch(s,"node%s(%S+)%s") do
    table.insert(t,node)
  end
  stemma[V::Manuscript.type] = t
-- Add edges to the stemma.
  for n1,n2 in string.gmatch(s,"edge%s(%S+)%s(%S+)%s") do
    maketrue(stemma[V::CopiedBy],{n1,n2})
  end
-- There are no more edges than the ones given.
  stemma[V::CopiedBy].cf = stemma[V::CopiedBy].pf
  return stemma
}

/** Create table of structures with sample data **/
procedure readSamples(stemma,sampletable) {
  local samples = {}
  for i,groupings in ipairs(sampletable) do
    local sample = newstructure(V,"sample"..tostring(i))
    sample[V::Manuscript.type] = stemma[V::Manuscript.type]
    sample[V::CopiedBy] = stemma[V::CopiedBy]
    sample[V::Variant.type] = range(1,#groupings)
  -- Add known equivalence relations to the sample.
    for variant,grouping in ipairs(groupings) do
      for _,element in ipairs(grouping) do
        maketrue(sample[V::VariantOf].graph,{element,variant})
      end
    end
    table.insert(samples,sample)
  end
  return samples
}

/** Show stemma using dot **/
procedure showStemma(stemmastring) {
  local f = assert(io.open("data/test.dot","w"))
  f:write(stemmastring)
  f:close()
  os.execute("dotty data/test.dot &")
}