[prog] Passing data between modules

[Jimen Ching]

On Mon, 28 Jul 2003, Dan Richter wrote:
>>I'm planning a suite of data quality control programs in C to run under
>>*NIX.  I want to keep everything as modular as possible in order to make the
>>suite flexible and futureproof.
>
>Hold it: you just wrote two conflicting sentences here. You want to write
>the program in C, and you want to make it modular, flexible and futureproof.
>
>Sorry to be so negative, but if you want to be futureproof, at least use
>C++. (Of course, you may have meant C generally, including C++.) Why is it
>so important to use C?

Can you elaborate on this?  Why are the two sentences conflicting?  And
why is C++ a better choice for futureproof?  Note, I'm not arguing against
using C++.  I too think C++ is a better choice, but note below.

Btw, what does futureproof mean anyway?

>I recommend a higher-level interpreted language: the program will be done
>five times faster and will be at least twice as readable, not to mention
>easier to change and less buggy. If you plan to do lots and lots of text
>processing, I recommend Perl. Otherwise, I recommend Python.

Five times faster?  Even if you have to learn a new scripting language
from scratch?  As you alluded to below, this doesn't sound like a small
project.  So, if the programmer is not familiar with a scripting language,
I'm not sure if learning a new langauge is appropriate for such a large
project.  This also applies to any language, not just scripting languages.

>>I'm concerned with passing data between the modules and how to do this
>>in a portable, accessible manner.
>
>This is something that C is really bad at. At least use C++.

Can you elaborate?  Data passing is not a language specific operation.  I
would imagine any language would be as good as any other language, unless
the language was designed specifically for data passing.

>If you really want to make all the modules separate programs (which I
>don't necessarilly recommend),

Is this because separate programs are intrinsically bad, or its bad only
for this application?  I would also like to know what your opinions are on
the Unix style of using pipes.  If a command line interface is acceptable
to Conor, the unix style of stringing together a list of utilities with a
pipe is exactly what he is describing.  For instance, the image
manipulation application called ImageMagic does this.

I don't know enough of the use cases to recommend any specific UI.  Just
trying to understand the pros and cons of the different approaches.

>you might try using Unix sockets for communication. This adds a lot of
>overhead (because all communications have to be serialized and
>deserialized), and in C it may make it more difficult to change the data
>structures later (because you have to change the serialization algorithm
>each time you change a data structure), but it's flexible means of
>message passing.

Why is it more difficult to change the data structures in C?  As opposed
to in any language that has to serialize the communication and have data
structures?

--jc
-- 
Jimen Ching (WH6BRR)      jching at flex.com     wh6brr at uhm.ampr.org