import torch


def neigh_diff_standard(bmus: torch.Tensor, positions: torch.Tensor) -> torch.Tensor:
    """
    Positional difference function.
    Computes index difference between Best Matching Units (`bmus`) and `positions`, where `positions` 
    are indices of elements inside the SOM grid.

    Parameters
    ----------
    bmus : torch.Tensor
        The list of Best Matching Units (2D indices)
    positions : torch.Tensor
        The 2D tensor of grid element indices 
    """
    return bmus - positions