mac (01/31/83)
More Notation
A^B is the cardinality of the functions B->A. 2^B is
card(characteristic functions B->2), which correspond to the
subsets of B (like the Pascal representation of sets).
Apparently the use of Beth cardinals is peculiar to one
author. The usual notation for the continuum is German
script c, or just c if that's all you can afford.
Puzzle
What's yellow and neither true not false?
Fun with ...
Proof that the universe is two's complement (as opposed to
one's complement or sign-magnitude). [Gosper, Item 154, MIT-
AI-239]
let x =: ...111111
then x+x = ....111110 = x-1
2*x = x-1
so x = -1, characteristic of two's complement machines
Be careful of arithmetic with "...".