r>blob</var> <var>k</var><code>)</code></dt><dt><code>(blob-s8-ref </code><var>blob</var> <var>k</var><code>)</code></dt><dd><p><var>K</var> must be a valid index of <var>blob</var>.</p><p><code>Blob-u8-ref</code> returns the octet at index <var>k</var> of <var>blob</var>.</p><p><code>Blob-s8-ref</code> returns the exact integer corresponding to the two's complement representation at index <var>k</var> of <var>blob</var>.</p></dd><dt><code>(blob-u8-set! </code><var>blob</var> <var>k</var> <var>octet</var><c