[Haskell-cafe] Re: SoC project: Python-Haskell bridge - request for feedback

[Don Stewart]

Remember that there are two proposals here, one potentially to the
Python team, one to the Haskell team . Of course the Haskell guys are
strongly interested in the use case Dan describes -- mitigating risk by
using Haskell for small components first, as part of larger legacy
systems.

The Python guys are more interested in Python use from Haskell, by the
looks of it.

-- Don


westondan:
> I notice that you omit from the advantages of calling Haskell from 
> Python what I consider the most important reason of all (at least from 
> the Haskell community side).
> 
> The choice of programming language (at least at the top level) is 
> primarily a political or managerial choice, not a technical one. Python 
> is not merely a "terrific glue language", it is often the "blessed" 
> language, and currently the language of choice in some industries, 
> including my own. This is not just "glue code" either: one in-house 
> application has about 100,000 lines of Python code (calling a comparable 
> amount of C++ code)!
> 
> Any hope of introducing Haskell into this realm requires a way to work 
> Haskell in slowly and from the bottom. As such I view your proposed 
> project as quite valuable, a robust and easy-to-use Python-Haskell 
> bridge (Python on top) being essential to growing the presence of 
> Haskell in non-academic circles.
> 
> Of course, it may be for this very political reason that you have 
> omitted the above from your list, in which case I completely understand. :)
> 
> Dan
> 
> Michał Janeczek wrote:
> >Hi,
> >
> >This is my second take on the project proposal.
> >I have expanded on a few points, and hopefully
> >also clarified a little bit.
> >
> >Please comment :)
> >
> >Regards,
> >Michal
> >
> >
> >Python-Haskell bridge
> >=====================
> >
> >Description
> >-----------
> >
> >This project will seek to provide a comprehensive, high level (and thus
> >easy to use) binding between Haskell and Python programming languages.
> >This will allow using libraries of either side from each language.
> >
> >If we decide to support function callbacks, these two functionalities
> >(embedding Haskell in Python, and vice versa) become interrelated.
> >In this light, it makes sense to implement them in the scope of the
> >same project.
> >
> >
> >Advantages of calling Haskell from Python
> >-----------------------------------------
> >
> >* Robust components
> >
> >    It might be beneficial to implement safety-critical componenets
> >    in a strongly, statically typed language. Since Python itself is
> >    a terrific "glue language", such components would usually be purely
> >    functional, leaving IO to the Python side.
> >    Embedding Haskell code in this way is of particular interest when
> >    there already is a large existing Python infrastructure. One can
> >    implement new functionality in a form of Haskell plugin/component,
> >    even if complete rewrite is not feasible.
> >
> >* Performance improvements for speed-critical code
> >
> >    Haskell compiled to native code is typically an order of magnitude
> >    faster than Python. Aside from that, advanced language features
> >    (such as multicore parallel runtime, very lightweight threads
> >    and software transactional memory) further serve to improve the
> >    performance. Haskell could become a safe, high level alternative
> >    to commonly used C extensions.
> >
> >* Access to sophisticated libraries
> >
> >    While its set of libraries is not as comprehensive as that of
> >    Python, Haskell can still offer some well tested, efficient
> >    libraries. Some of the examples might be:
> >
> >    * rich parser combinator libraries (like Parsec)
> >    * persistent, functional data structures (i.e. Data.Map,
> >          Data.IntMap, Data.Sequence, Data.ByteString)
> >    * QuickCheck testing library to drive analysis of Python code
> >
> >
> >Advantages of calling Python from Haskell
> >-----------------------------------------
> >
> >* Python as a scripting language for Haskell applications
> >
> >    Python is widely considered to be more approachable for regular
> >    users. As such, it could be used as a configuration/extension
> >    language for applications that benefit from extra flexibility.
> >    One example of such application is xmonad window manager.
> >
> >* Access to a large number of libraries
> >
> >    As a much more popular language, Python has built up an impressive
> >    suite of libraries. There already are Haskell projects which rely
> >    on Python code to implement missing functionality, for example
> >    a paste bin application hpaste, which uses Pygments syntax coloring
> >    library.
> >
> >
> >Deliverables
> >------------
> >
> >* A low level library to access and manage Python objects from Haskell
> >
> >* Library support for wrapping Haskell values in Python objects. This
> >  is necessary to allow function callbacks. In addition, thanks to that
> >  feature large and/or lazy data structures can be efficiently passed
> >  from Haskell to Python
> >
> >* A set of low level functions to convert built-in data types between
> >  Haskell and Python (strings, numbers, lists, dictionaries,
> >  generators etc.)
> >
> >* A high level wrapper library for Haskell that simplifies embedding
> >  and calling Python code
> >
> >* A set of functions, and possibly a tool, to wrap up monomorphic
> >  functions and expose them to Python through foreign export facility
> >
> >* A way (an external tool, or a Template Haskell macro) to easily
> >  derive conversion functions for user-defined data types/objects
> >
> >* Documentation and a set of examples for all of above
> >
> >
> >Optional goals
> >--------------
> >
> >In order of increasing amount of work and decreasing priority:
> >
> >* Exporting a wider class of functions to Python
> >
> >* A Python module that inspects a compiled Haskell module and
> >  transparently exposes functions within. This might be possible
> >  thanks to GHC API
> >_______________________________________________
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> >Haskell-Cafe at haskell.org
> >http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
> >
> 
> 
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