changePiece
Changes the piece at the specified coordinate by swapping its color from 'B' to 'W' or vice versa.
Return
A new board with the piece color swapped at the specified position.
Parameters
coordinate
The coordinate of the piece to change.
Throws
if the coordinate is out of bounds or if there is no piece at the position.
Changes the piece at the specified linear index by swapping its color.
Return
A new board with the piece color swapped at the specified index.
Parameters
idx
The linear index of the piece to change.
Throws
if the index is out of bounds or if there is no piece at the position.