Programming Languages Project

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Revision as of 08:04, 14 April 2006 by Ajolma (talk | contribs) (→‎R)
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note: this is the quick first draft, please feel free to refactor and add, but when adding, consider linking to other pages first, or creating a new page on this wiki

Goals

This project is intended for information about how different programming languages are used in OSG software and what's available.

A specific interest for this project is to discuss how to enhance or achieve interoperability between libraries and tools written in different languages.

I'm not sure if there should be an official committee for this (probably not), but I think this kind of project is needed as it serves for example the educational project and developers.

Audience

The contents are inteded for beginning developers who are looking for basic information and pointers, and for more seasoned developers who may not be well informed what's happening among languages they are not using.

Libraries

Geospatial software libraries provide the functionalities that belong to general categories of

  • Data management (DM)
  • Analysis (A)
  • Visualization (V)

The codes DM, A, and V codes are used below. In practical tools the specialized geospatial software have to be linked to general software libraries and toolkits like GUI toolkits, network software, etc.

Interoperability

  • Maintain functionally equivalent libraries in two languages (JTS/GEOS)
  • Use Swig (GDAL, GEOS)
  • Use .Net/mono (MapWindow)

Using Swig

  • How to achieve a robust mapping between memory management in low level language and in the interface language?

The problem is that in low level language the programmer usually explicitly deletes an object (smart pointers are an exception) and in a scripting language the programmer usually doesn't. The binding should somehow make sure that all low level objects exist as long as they are needed but not longer. Different schemes exist in both worlds for managing this, but their interaction may make the problem even worse, especially when a single binding code (swig) should take care of it.

This problem exists for example in GDAL, where things like

band = gdal::Open('filename').GetRasterBand(0)

usually result in bad objects.

C, C++, Fortran and other "low-level" languages

  • Many fundamental libraries are written in these languages
  • These can be wrapped efficiently with Swig

Java

Java is a hybrid in the sense that it's used for fundamental libraries but it is also often preferred also for its high-level features (strong OO). Notable Java OSG include JTS, uDig, ...

Scripting languages

Scripting languages take the burden of memory management and compilation and linking off from the developer.

Perl

todo:

  • Perl bindings for GEOS

PHP

PHP stands for "PHP: Hypertext Preprocessor" and is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. Its syntax draws upon C, Java, and Perl, and is easy to learn. The main goal of the language is to allow web developers to write dynamically generated webpages quickly, but you can do much more with PHP. (from the PHP manual preface)

Python

R

R is a language for statistical computing.

Ruby