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From: Johan Råde (rade_at_[hidden])
Date: 2008-05-05 11:10:09

John Maddock wrote:
> So, it looks like so far we have:
> next(val)
> prior(val)
> and either of
> representation_distance(a, b);
> discrete_distance(a, b);

I'm still a bit unhappy about calling a signed quantity a "distance".
I would prefer "difference". Let me elaborate:

To me a "distance" is a quantity that satisfies the rules:

d(x,y) >= 0
d(x,x) = 0
d(y,x) = d(x,y)
d(x,y) + d(y,z) >= d(x,z)

while a "difference" is a quantity that satisfies the rules

d(x,x) = 0
d(y,x) = -d(x,y)
d(x,y) + d(y,z) = d(x,z)

The function we are discussing satisfies the second set of rules.


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