An attribute is just a key-value pair, for example "shape" := "box". Attributes are used to specify the style of graph elements during export.

The record Style a s specifies the style to use when exporting a graph in the DOT format. Here a is the type of the graph vertices, and s is the type of string to represent the resulting DOT document (e.g. String, Text, etc.). Most fields can be empty. The only field that has no obvious default value is vertexName, which holds a function of type a -> s to compute vertex names. See the example for the function export.

Default style for exporting graphs. All style settings are empty except for vertexName, which is provided as the only argument.

Default style for exporting graphs whose vertices are Show-able. All style settings are empty except for vertexName, which is computed from show.

defaultStyleViaShow = defaultStyle (fromString . show)

Export a graph with a given style.

For example:

style :: Style Int String
style = Style
    { graphName               = "Example"
    , preamble                = ["  // This is an example", ""]
    , graphAttributes         = ["label" := "Example", "labelloc" := "top"]
    , defaultVertexAttributes = ["shape" := "circle"]
    , defaultEdgeAttributes   = mempty
    , vertexName              = \x   -> "v" ++ show x
    , vertexAttributes        = \x   -> ["color" := "blue"   | odd x      ]
    , edgeAttributes          = \x y -> ["style" := "dashed" | odd (x * y)] }

> putStrLn $ export style (1 * 2 + 3 * 4 * 5 :: Graph Int)

digraph Example
{
  // This is an example

  graph [label="Example" labelloc="top"]
  node [shape="circle"]
  "v1" [color="blue"]
  "v2"
  "v3" [color="blue"]
  "v4"
  "v5" [color="blue"]
  "v1" -> "v2"
  "v3" -> "v4"
  "v3" -> "v5" [style="dashed"]
  "v4" -> "v5"
}

Export a graph whose vertices are represented simply by their names.

For example:

> Text.putStrLn $ exportAsIs (circuit ["a", "b", "c"] :: AdjacencyMap Text)

digraph
{
  "a"
  "b"
  "c"
  "a" -> "b"
  "b" -> "c"
  "c" -> "a"
}

Export a graph using the defaultStyleViaShow.

For example:

> putStrLn $ exportViaShow (1 + 2 * (3 + 4) :: Graph Int)

digraph
{
  "1"
  "2"
  "3"
  "4"
  "2" -> "3"
  "2" -> "4"
}