iamax

import mir.ndslice.allocation: slice;
auto x = slice!double(6);
//     0  1   2   3   4  5
x[] = [0, -1, -2, -3, 3, 2];
assert(iamax(x) == 3);
// -1 for empty vectors
assert(iamax(x[0 .. 0]) == -1);

import mir.ndslice.allocation: slice;

auto x = slice!cdouble(4);
//        0          1          2         3
x[] = [0 + -1i, -2 + 3i, 2 + 3i, 2 + 2i];

assert(iamax(x) == 1);
// -1 for empty vectors
assert(iamax(x[$ .. $]) == -1);