On 2/14/11 3:44 PM, Stephen Bloch wrote:
On Feb 14, 2011, at 3:26 PM, David Van Horn wrote:
On 2/14/11 3:14 PM, Sam Tobin-Hochstadt wrote:
No, it's not a bug. Since 1e100 is an inexact number, there's
uncertainty about the minimum of those two numbers, and the result is
therefore inexact.
I would've expected min to return a number that is `eq?' to one of its
arguments.
In other words, what is wrong with this definition of `min'?
(define (min n1 n2)
(cond [(<= n1 n2) n1]
[else n2]))
What's wrong with this is that, mathematically, since 1e100 is inexact, we're not CERTAIN it's>= 0, so
the "proper" answer to (<= n1 n2) is not true but rather almost-certainly-true. (An
"inexact Boolean", if you will....)
When you define the function as above, the "<=" takes its best guess as to
which number is really smaller and pretends that the answer is certain.
Then what is the correct definition?
David
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