Right here on day 328 Casey implemented the U64ToASCII function as part of the printf replacement, and added the following assert to catch the case where there would be a divide by zero error since the loop in that function advances by diving Value by Base while Value != 0.

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Assert(Base != 0);


However, if Base is 1 then the loop never stops since dividing by 1 doesn't do anything. The assert should probably be changed to something like the following.

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Assert(Base > 1);


Side note, just after adding that assert, Casey wondered aloud whether there was such a thing as base zero. As far as I know there is not, but surprisingly negative bases are a thing! Some early Polish computers even used negabinary (base -2).