Puzzle - RPL and others

[3298]

Another private message from Albert Chan, another bug uncovered ... and now fixed. This one is very subtle.
Before:

Code:

bitset_t digit_bitset = 1 << (digit - 1);

After:

Code:

bitset_t digit_bitset = ((bitset_t) 1) << (digit - 1);

Without this typecast, it breaks for bitshifts greater than or equal to the number of bits in an int (typically 32 bits), which would be encountered on bases higher than 32. C isn't being very friendly here.
But that's the benefit of having an alternative implementation to compare to, since it's quite hard to verify the results by hand: discrepancies between them uncover bugs in one or the other. Thank you for not simply believing my results!