[Numpy-discussion] C vs. Fortran order -- misleading documentation?
Francesc Alted
faltet@pytables....
Wed Jun 9 02:16:33 CDT 2010
A Tuesday 08 June 2010 23:34:09 Anne Archibald escrigué:
> > But the issue isn't one of efficiency, it's merely an arbitrarily chosen
> > convention. (Does anyone know the history of the choices for FORTRAN and
> > C, esp. why K&R chose the opposite of what was already in common usage in
> > FORTRAN? Just curious?)
>
> This is speculation, not knowledge, but it's worth pointing out that
> there are actually two ways to represent a multidimensional array in
> C: as a block of memory with appropriate type definitions, or as an
> array of pointers to subarrays. This latter approach is generally not
> used for numerical work, but is potentially useful for other
> applications. More relevantly, it already has a natural syntax;
> a[2][3][5] naturally follows the chain of pointers and gives you what
> you want; it also forces your last index to change most rapidly as you
> walk through memory. So it would be very odd if multidimensional
> arrays defined without pointers but using the same syntax were indexed
> the other way around. (Let's ignore abominations like 5[3[2[a]]].)
Hey, maybe it is only speculation, but this is the most convincing argument
for breaking Fortran convention that I've ever heard (although I'm not sure if
C was really breaking Fortran convention, as both languages should have born
more or less in time, although I'd say that Fortran is a bit older).
--
Francesc Alted
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