here - Stefan-Marr.de

2.1. Multi-Language Virtual Machines
guage designers and implementers, who built hundreds of languages on top
of them. 4,5
Often the motivation for such language implementations is to fill a particular
niche in which the language-specific properties promise higher productivity,
even when the performance might be sacrificed. Another motivation
might be adoption. While a new language with its own runtime typically
lacks tooling and libraries for productive use, targeting an existing platform
such as the JVM and CLI can ease the integration with existing systems, and
thus, facilitate adoption. To give a single example, Clojure 6 integrates well
with the ecosystem of the JVM, which enabled adoption and brought concurrent
programming concepts such as agents, atoms, and software transactional
memory to a wider audience.
Support for dynamic languages was extended to strengthen VMs as general
purpose platforms. Over the years, the JVM and CLI grew into fully
adopted general purpose platforms and with their success grew the adoption
of new JVM and CLI languages. This motivated efforts to reduce the performance
cost of dynamic languages. The various method dispatch semantics of
dynamic languages were one of the largest performance concerns. To improve
the situation, the JVM specification was extended by infrastructure around
the new invokedynamic bytecode [Rose, 2009; Thalinger and Rose, 2010],
which gives language designers a framework to specify method dispatch semantics
and enables the just-in-time compiler to optimize the dispatch for
performance. With the Dynamic Language Runtime for the CLI, Microsoft went
a different route and provides a common dynamic type system and infrastructure
for runtime code generation. However, both approaches have in common
that they extend the reach of the underlying platform to new languages, and
thus application domains.
Multi-language VMs are targets for library and language implementers.
With the additional infrastructure for dynamic languages in place, the JVM
and the CLI became multi-language VMs. While the notion has been used
4 A list of languages targeting the .NET Framework, Brian Ritchie, access date: 28 September 2012
http://www.dotnetpowered.com/languages.aspx
5 Programming languages for the Java Virtual Machine JVM and Javascript, Robert Tolksdorf, access
date: 28 September 2012 http://www.is-research.de/info/vmlanguages/
6 http://clojure.org
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