Re: Standard Ada Preprocessor

[Jeffrey Carter <spam@spam.com>]

Marin David Condic wrote:

> You aren't fundamentally changing the problem - just where it will be 
> dealt with. If the argument against conditional compilation is that it 
> will make ugly, incomprehensible code, then that same argument goes 
> against the build process. It is, after all, some set of instructions 
> that will be obeyed by the computer and hence a kind of programming 
> language, so giving *it* the responsibility is just going to result in 
> ugly, incomprehensible code at the build level. 

There's a general SW engineering principle called localization. You 
don't lump your code for dealing with a 4-line LCD display in with the 
code for dealing with a temperature sensor just because they're both 
hardware. Similarly, you shouldn't want your code for doing something 
platform dependent on one platform lumped in with your code for another 
platform, nor your code for doing things lumped in with your code for 
deciding which code to use for this build.

Separating concerns this way makes everything easier to understand. I 
can look at the code for dealing with a VMS file system without having 
to understand the code for selecting a VMS file system; I can look at 
the code for selecting the file system without having to look at the 
code for dealing with file systems.

That said, it would be nice to have a standard, portable way to select 
different bodies for a build, but even without it, the advantages of 
separating these independent concerns seem clear.

-- 
Jeff Carter
"Many times we're given rhymes that are quite unsingable."
Monty Python and the Holy Grail
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