- This is Guy L. Steele Jr.'s recursive quadrant-swapping algorithm for Boolean matrix transposition.
- The matrix is 64x64 with 1-bit elements and is represented by an array of sixty-four 64-bit integers.
- The matrix is row-major: Each row is one 64-bit integer. Column 0 is the least-significant bit.
- The top-right quadrant (low row, high column) is swapped with the bottom-left (high row, low column).
- The same operation is then applied to each quadrant recursively until each quadrant is a single bit.

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