error: lvalue required as left operand of assignment

[Kai Yan]

Trying to do this:

FloatD arr = {1.f,3.f,2.f,5.f,6.f,2.f,6.f};
FloatD t = 0.0f;
set_requires_gradient(t);

arr[2] = arr[2] + t
(error: lvalue required as left operand of assignment)

[Sebastien Speierer]

You will need to use mask-assignement for this. Something like this:

mask_t<FloatD> mask = {0, 1, 0, 0, ...};
arr[mask] += t;

You could also use arange to craft some fancier masks based on indexing.

[Sebastien Speierer]

Please note that you will often find answers to such questions by reading the documentation carefully. We would like to keep github issues for actual issues/bugs with the library 😉