def get_nonmatching_blocks(matching_blocks):
i = j = <NUM_LIT:0><EOL>for match in matching_blocks:<EOL><INDENT>a, b, size = match<EOL>yield (i, a, j, b)<EOL>i = a + size<EOL>j = b + size<EOL><DEDENT>
Given a list of matching blocks, output the gaps between them.

    Non-matches have the format (alo, ahi, blo, bhi). This specifies two index
    ranges, one in the A sequence, and one in the B sequence.