Travis Oliphant wrote: > I'm talking about arrays of pointers to other arrays: > > i.e. if somebody defined in C > > float B[10][20] > > then B would B an array of pointers to arrays of floats.
No, it wouldn't, it would be a contiguously stored 2-dimensional array of floats. An array of pointers would be float *B[10]; followed by code to allocate 10 arrays of 20 floats each and initialise B to point to them. > Yes, I saw that. But, it could actually be supported, in general. Certainly it *can* be supported, but the question is how many different format variations it's reasonable to expect the consumer of the data to be able to deal with. Because each variation requires the consumer to use different code to access the data, if it wants to avoid making a copy. > else if (ndims == 3) > > var = (float ***)segments > for (i=0; i<shape[0]; i++) > for (j=0; j<shape[1]; j++) > for (k=0; j<shape[2]; k++) > # process var[i][j][k] This assumes that the 3-dimensional case is using the array-of-pointers implementation at all levels. But there are other possibilities, e.g. a 1d array of pointers to contiguous 2d arrays, or a contiguous 2d array of pointers to 1d arrays. It's hard to deal with all of those using a common piece of code. I can imagine cases like that coming up in practice. For example, an image object might store its data as four blocks of memory for R, G, B and A planes, each of which is a contiguous 2d array with shape and stride -- but you want to view it as a 3d array byte[plane][x][y]. (Actually you'd probably *prefer* to view it as byte[x][y][plane], which would make things even more difficult...) > I was thinking more of a C-iterator, like NumPy provides. This can be > very efficient (as long as the loop is not in Python). > > It sure provides a nice abstraction that lets you deal with > discontiguous arrays as if they were contiguous, though. Something like that might be useful. -- Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | Carpe post meridiem! | Christchurch, New Zealand | (I'm not a morning person.) | [EMAIL PROTECTED] +--------------------------------------+ _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
