in reply to boolean calculation with very large data

See vec. By using bitstrings instead of bytestrings, your masks will be 1/8th the size (and the boolean operations a lot faster).

With a million random generated intervals, using bytestrings consumed nearly 2 GB and 80+ seconds; the same intervals using bitstrings only 0.6GB and 40 seconds. 

C:\test>797136-a -INTERVALS=1e6
Check mem: 1.975 GB ( 82 seconds )

C:\test>797136-b -INTERVALS=1e6
Check mem: 0.616 GB ( 44 seconds )

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BTW: Yourcodewouldbealoteasiertoreadandeditifitcontained a few spaces!

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