[lug] Learning to code on Linux.

[Bear Giles]

I'm going to take a contrary voice here.
> A friend called me today to ask about getting the source for libc.  I 
> installed Linux for him but didn't include the source packages.  He 
> wants to rewrite a FORTRAN app in C, so that it will be more portable 
> and maintainable down the road.  He has little experience with Linux.
I think the key words here are PORTABLE and MAINTAINABLE.  Like many 
other people here I have worked with scientists who picked up a C book 
and were convinced they could write C apps just because they got their 
stuff to compile.  It might have compiled, but it was clearly "Fortran 
in C".  It was just as bad as "Pascal in Ada" (1980s) and even, shudder, 
the "Fortran in Ada" I saw a few times at a defense contractor.

Anyone with experience in one procedural language can write something 
that compiles in another procedural language in a few days to a few 
weeks.  But it's at least six months until you write stuff that doesn't 
consistently make you flinch later, and probably at least two years 
until you can do something truly portable and maintainable.  You can't 
do the latter until you understand at a deep level how other people will 
approach the code.

To be honest the best answer may be learning how to use the gcc Fortran 
tool chain under Linux and cleaning up the code in a language he knows 
well.  Bring it up to the latest version of Fortran, fix all warnings, 
use modern naming conventions instead of one- or two-character variable 
names for anything other than loop indexes and the like.  It should also 
be possible to use Fortran/C bindings, especially if everything is 
handled by the gcc tools. GCC has changed the game entirely since they 
have multiple front-ends to the compiler -- I seem to recall it offering 
C/C++, java, fortran, ada, more.
> So, I can get him the source.  He said, "if I have the source it will 
> answer all my questions about libc, and probably teach me what I need 
> to write my app."  He's not scared of doing hard work to gain a skill.
Reading the libc source will tell him how to write a C library.  That's 
not what he wants to do.  He wants to port a Fortran app.  To see how to 
do that, he should look at the source code of similar apps that are 
already written in C, and ideally review them with a friend who's both C 
literate and scientifically literate so the friend can point out bad C 
practices while understanding what the author was trying to do.
> But I wonder what might be more efficient for him.  A study group or 
> book might be a big help.  Unfortunately he doesn't get around at all 
> and has dial-up Internet.
There's the classic "Numerical Methods in C".
> I expect he can figure out gcc, make, etc, but might need some help 
> with the easiest way to get source packages, how to use -dev packages, 
> etc.
There should be 'hello world' demonstrations for all of the standard 
portable tools, at least under Debian/Ubuntu.  It's basically an empty 
project that does nothing but has all of the configuration files set up 
to do autoconf, automake, and then package as a .deb package.  You just 
have to add your source and set up the build process.  "just" hee hee.

Bear