I'm pleased to announce the first public release of Ministg. Ministg is an interpreter for a high-level, small-step, operational semantics for the STG machine. The STG machine is the abstract machine at the core of GHC. The operational semantics used in Ministg is taken from the paper "Making a fast curry: push/enter vs. eval/apply for higher-order languages" by Simon Marlow and Simon Peyton Jones. Ministg implements both sets of evaluation rules from the paper. One of the main features of Ministg is the ability to record a trace of the execution steps as a sequence of html files. And example trace can be viewed here:  http://www.cs.mu.oz.au/~bjpop/trace/step0.html The example shows the execution of a program which sums a list of three integers, using the well-known space-leaky version of sum. Follow the "next" and "previous" links to step forwards and backwards through the trace. The main reason I wrote Ministg is to explore various extensions to the STG machine. The current release features a simple extension in the form of call-stack tracing, which is strongly influenced by the cost-centre stacks of GHC. I expect it will also be a useful tool for people who are interested in learning more about the STG machine. More detailed information is available from the haskellwiki page:  http://www.haskell.org/haskellwiki/Ministg You can download it from hackagedb:  http://hackage.haskell.org/package/ministg Or you can get the latest code from patch-tag:  darcs get http://patch-tag.com/r/ministg/pullrepo ministg Cheers, Bernie.