Choice of Programming Language

  We cannot decide for a programming language based on the News Cache's design alone because the programming language has to fulfill the following criteria:

Availability

The programming language must be available on a wide set of platforms since the News Cache should be available for as many platforms as possible. In addition free implementations of the chosen language should exist, since we want to make this software freely available under the terms of the Gnu Public License (<http://www.fsf.org/copyleft/gpl.html>).

Acceptance

The programming language has to be widely accepted since the user installing the News Cache should be able to compile the source code (binaries cannot be made available for all systems) and be able to apply minor code fixes in case of problems.

Optimization

Compilers producing highly optimized code should be available. Interpreted languages usually have a worse performance, because of the interpreter's overhead. Hence we will not consider languages where only interpreters are available (such as Perl [WCS96], Python ([vR97] and [Lut96]), Tcl [Ous94] and others).

The following languages fulfill these requirements.

C

The GNU C Compiler , a freely available and well optimizing C compiler as well as commercial C compilers are available for nearly any platform. C has the advantage that it is widely accepted and that most NNTP Software (e.g., INN [Sal92], tin, etc.) is written in C. One disadvantage of C is that it is neither object-based nor object-oriented. This makes it difficult to write objects with similar behavior without unnecessarily duplicating the source code.

To test the suitability of C we wrote a small news cache with very basic functionality only. Even this small program got rather complex. We had to decide whether to implement lists for several types or to use only one list structure and make heavy use of the cast operator. Both methods are error prone.

C++

The GNU C++ Compiler , a freely available, optimizing C++ compiler as well as commercial C++ compilers are available for most platforms. C++ has the advantage that it is object-oriented and allows to define algorithms and objects in a type independent way using templates. Unfortunately C++ is not as widely available and accepted as C. Since C++ has completely been standardized only a short time ago [ES90], many C++ compilers do not implement all aspects of the C++ standard.

To test the suitability of C++, we ported our test program written from C to C++. As expected the code to handle different types of lists got smaller and was easier to understand.

Java

Java is a relatively new programming language that has been introduced by Sun Microsystems ([GJS97] and [AG97]). Java is similar to C++, except that pointers have been eliminated and the explicit memory allocation has been replaced by an implicit one as found in Lisp or Prolog. Its advantage is that compilers for an abstract machine and for native code exists. This means that the News Cache can be run without compiling the source code on any computer where the interpreter for the Java Virtual Machine is available. However, with the cost of much performance.

For our implementation we have chosen to use C++ in favor of Java, since C++ compilers are wider available and have a much better performance and acceptance.

Other languages like Objective C, Smalltalk , Pascal, Modula 2, and similar languages have not been considered, because of their restricted availability and acceptance.