Reduction functions for matrices? about linalg HOT 2 CLOSED

Extending the fold functions over matrices shouldn't be too hard.

argmax() is a trickier case. I've painted myself into a bit of a consistency corner. maxelem(a) is defined as a[argmax(a)] for vectors, there's a nice symmetry between argmax returning an int and operator[] taking an int. argmax on a matrix COULD return the index of the "greatest" column, as linalg::vec does model LessThanComparable, but this seems a little nonsensical and not very useful. A matrix is semantically quite a bit different from a sequence of vectors.

argmax could return the index of the greatest element as though the matrix were a flat array in column major order. I do define a few other operations on matrices (comparison ops, etc.) as though they were a flat sequence of numbers, but I don't have any sort of function for "flat indexing" into a linalg::mat.

I suppose argmax could return an int2, and I could add an overload of operator[] which accepts an int2. The only remaining question is whether mat[{x,y}] should be equal to mat[x][y] (less confusing) or mat[y][x] which would match the sort of "row,column" subscripting you see in math textbooks.

I'll do the fold functions right away, and I welcome your input on what would be most logical for something like argmax.

from linalg.

I'm going to close this issue for now, as the obvious improvements were made and there was no further input on the argmax semantics.

from linalg.