in reply to
FWIW Perl 6 solves this problem by doing math in rational numbers by default:
$ perl6 -e 'say -53.80 + 46.70'
See also: What Every Computer Scientist Should Know About Floating-Point Arithmetic and rats and other pets.
By rote learning.
Via Genetic memory.
It's provided by my firmware.
I just remember them.
Thirty days hath September
My computer gets it right, usually.
I just ask someone else.
Someone punches me on the first of the month.
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