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archive of pyvm.git (last push: version 2.1). includes "lightweight C++" in pyvm/lwc dir.
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What is pyvm ------------ It's a reimplementation of various userspace programs under a common dynamic language runtime system. What's special about pyvm is that this dynamic runtime is not a general purpose vm/language; it's not supposed to be used by code outside the project and for that it does not have backwards compatibility. The various implemented userspace programs are the only testcase that drives the evolution of the vm. Similarily, various libraries do not have fixed public APIs and so it's easier to make temporary implementations that can be used in order to bootstrap something else, and be refactored later. The core vm is a cousing of python and can even run small python programs, but 100% compatibility and passing python's test suite is not a goal. Using a dynamic language offers some very important advantages like: automatic memory managment, no segfaults, exceptions, stackless threading, no need for recompilation, and generally the common runtime object system that can be used for very powerful and flexible inter-library APIs. On the other hand, pyvm likes C and based on the theory that 90% of the time of a program is spent in 10% of the code we try to move that part of the code in C and have the core program control in the scripting language; this has turned out to work very well (and at times even better than Just In Time compilation) pyvm does a *lot* of things and it's a tool that makes creating applications easy. However, it's not supposed to actually replace the existing userspace toolchains any time soon. It is more like a half-finished hobby project that may be suitable for people who prefer to use software they have written and can easilly modify. Existing userspace systems have some problems. One of them is very often the "dependancy hell" where building the entire system from the sources is nearly impossible and one has to use a prebuilt binary distribution. Another problem is that their source code is several millions of lines of code and thus it's impossible for a programmer to review the entire code; programmers can only focus on a part of the system. Finally, those systems are made with the use of many independant components (although some times programmers are forced to write something as a library because of the fact that there is no standard GUI in UNIX and since they can't master all toolkits, leave the frontend of their program to someone else). With this approach, libraries try to predict everything the user will need in a complicated API, that's both hard to learn and still not always sufficient, not to mention hard to test and a pain to maintain the backwards compatibility. Just like UNIX has a well defined "libc" that amongst other things provides the ability to read/write to the terminal, the Next Level should have a standard library to a GUI toolkit (this is almost 2010!). However, for one, standarizing a GUI toolkit is much harder. The C programming language is not good enough for this task and the systen would also have to standarize a higher level object model that makes using the GUI easier. However, standarizing a dynamic runtime system is even harder, because unlike C which was guided by the CPU opcodes, a dynamic language vm is much more vague and we cannot predict what we can expect from it, unless there are many programs that use it. pyvm is bootstrapping an experimental "Next Level System" where the dynamic language, the object model, script recompilation, graphical user interface, font engine, etc, are part of the core system. Application not only use it, but also give feeback for the ehnancement of these core components. Currently, pyvm is made of about 300 scripting files (python & pe) in 70k lines of code and 12k lines of mini C libraries. The base vm is written in about 30k lines of C. The fact that backwards compatibility can be broken does not mean that it is broken every day; the project is supposed to stabilize and the APIs properly documented. This all may sound great and all, but the fact is that it is not so great actually. What's presented above in this document is the theory of the project. In practice the reimplemented userspace programs are far from perfect and their main value the the extreme simplification of things. So it's supposed to interest people who believe that "being a user is boring" or want to play with a miniature of the existing userspace. A list of the various userspace prorgams that can be performed by pyvm can be seen in Doc/APP-LIST.txt The rest -------- Initial version of pyvm is Copyright (C) 2005-2009 Stelios Xanthakis pyvm is distributed under the terms of the GNU GPL pyvm uses code from various people. Please see Doc/CREDITS.txt Home page: http://students.ceid.upatras.gr/~sxanth/pyvm-2.0/ Git repo: http://students.ceid.upatras.gr/~sxanth/pyvm.git e-mail: sxanth@ath.forthnet.gr (must contain the word "pyvm")
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