This is the top-level module for the graphviz library. It provides functions to convert Graphs into the Dot language used by the Graphviz suite of programs (as well as a limited ability to perform the reverse operation).

Information about Graphviz and the Dot language can be found at: http://graphviz.org/

There are various functions available for converting Graphs to Graphviz's Dot format (represented using the DotGraph type). There are two main types: converting plain graphs and converting clustered graphs (where the graph cluster that a particular Node belongs to is determined by its label).

These functions have two versions: one in which the user specifies whether the graph is directed or undirected (with a Bool value of True indicating that the graph is directed), and a primed version which attempts to automatically infer if the graph is directed or not. Note that these conversion functions assume that undirected graphs have every edge being duplicated (or at least that if there exists an edge from n1 to n2, then n1 <= n2; if n1 > n2 then it is removed for an undirected graph).

The following functions provide support for passing a Graph through the appropriate GraphvizCommand to augment the Graph by adding positional information, etc.

Please note that there are some restrictions on this: to enable support for multiple edges between two nodes, the Comment Attribute is used to provide a unique identifier for each edge. As such, you should not set this Attribute for any LEdge.

For unprimed functions, the Bool argument is True for directed graphs, False otherwise; for the primed versions of functions the directionality of the graph is automatically inferred. Directed graphs are passed through Dot, and undirected graphs through Neato. Note that the reason these functions do not have unsafePerformIO applied to them is because if you set a global Attribute of:

    Start (StartStyle RandomStyle)

then it will not necessarily be referentially transparent (ideally, no matter what the seed is, it will still eventually be drawn to the same optimum, but this can't be guaranteed). As such, if you are sure that you're not using such an Attribute, then you should be able to use unsafePerformIO directly in your own code.

This section contains convenience functions for quick-and-dirty augmentation of graphs. No Attributes are applied, and unsafePerformIO is used to make these normal functions. Note that this should be safe since these should be referentially transparent.

This section allows you to manually augment graphs by providing fine-grained control over the augmentation process (the standard augmentation functions compose these together). Possible reasons for manual augmentation are:

• Gain access to the intermediary DotRepr used.
• Convert the default DotGraph to a GDotGraph (found in Data.GraphViz.Types.Generalised) so as to have greater control over the generated Dot code.
• Use a specific GraphvizCommand rather than the default.

Note that whilst these functions provide you with more control, you must be careful how you use them: if you use the wrong DotRepr for a Graph, then the behaviour of augmentGraph (and all functions that use it) is undefined. The main point is to make sure that the defined DotNode and DotEdge values aren't removed (or their ID values - or the Comment Attribute for the DotEdges - altered) to ensure that it is possible to match up the nodes and edges in the Graph with those in the DotRepr.