Sankel Software is pleased to announce the release of TinyLaunchbury 1.0.1 [1], a small implementation of John Launchbury's natural semantics for call-by-need. We hope that is is useful in helping to understand how call-by-need works.
There is also a new blog post[2], explaining the semantics, the code and why the semantics are useful to understand.
Elliot Stern
Sankel Software
[1] http://hackage.haskell.org/package/TinyLaunchbury
[2] http://netsuperbrain.com/blog/posts/haskells-evaluation-isnt-magic/