siren-hs

siren-hs is a Haskell library and CLI for building directed flowchart-style graphs and rendering them to SVG.

The project includes:

• A typed graph model in src/Siren/Types.hs
• A composable EDSL for graph construction in src/Siren/EDSL.hs
• Two layered layout engines:
  • Sugiyama-like (src/Siren/Layout/Sugiyama.hs)
  • Dagre-style (src/Siren/Layout/Dagre.hs)
• An SVG renderer based on diagrams-svg in src/Siren/Render/SVG.hs
• A CLI application with sample graphs in app/Main.hs and app/Samples.hs

Features

• Node shapes: rectangle, rounded rectangle, diamond
• Directed edges with optional labels
• Two layout strategies for hierarchical diagrams
• Layout direction support (TopDown, LeftRight) in the library APIs
• Batch rendering of all built-in sample graphs

Installation and build

This project uses Stack.

stack build

Run tests:

stack test

CLI usage

The executable expects a graph name and optionally a layout engine.

stack run -- GRAPH_NAME [--layout ENGINE]

Short option for layout:

stack run -- GRAPH_NAME -l ENGINE

Where:

• ENGINE is sugiyama (default) or dagre
• Output is written to output/<graph>-<engine>.svg

Available graph names

• sample
• bugged
• chain
• diamond-merge
• fan-in
• crossing-bipartite
• long-label
• multi-source-sink
• cycle
• dense-layered
• disconnected
• ladder

Render one graph

stack run -- sample
stack run -- long-label --layout dagre

Render all built-in samples with both engines

stack run -- all

This generates 24 SVG files (12 samples x 2 engines) in output/.

Library usage

Import the top-level Siren module:

import Siren

Common convenience functions:

• writeGraphSvg :: FilePath -> Direction -> Graph -> IO ()
• writeGraphSvgDagre :: FilePath -> Direction -> Graph -> IO ()
• writeGraphWith :: (LayoutEngine engine, RenderEngine renderer LaidOutGraph) => engine -> renderer -> FilePath -> Graph -> IO ()

Minimal example:

import Siren

main :: IO ()
main =
	case buildGraph (node "start" "Start" <> node "end" "End" <> edge "start" "end") of
		Left err -> putStrLn err
		Right g -> writeGraphSvg "output/example.svg" TopDown g

Project structure

• src/Siren.hs: top-level public API
• src/Siren/Types.hs: core graph types
• src/Siren/EDSL.hs: graph construction DSL
• src/Siren/Layout/*.hs: layout engines and shared layout types/utilities
• src/Siren/Render/SVG.hs: SVG rendering backend
• app/Main.hs: CLI entry point
• app/Samples.hs: sample graphs used by the CLI
• test/: test suite (tasty, tasty-hunit, tasty-quickcheck)

Development notes

This repository uses package.yaml (hpack) as the source of truth.

• Edit package metadata and dependencies in package.yaml
• Let Stack/hpack regenerate siren-hs.cabal
• Avoid manual edits to generated Cabal fields