Re: [Chicken-users] Numbers weirdness

[John Cowan]

Andy Bennett scripsit:

> #;5> (log2 (expt 2 251))
> 251.0
> #;6> (ceiling (log2 (expt 2 251)))
> 252.0
> 
> Is it just late on a Friday? Am I crazy?

Trying (log2 (expt 2 251)) in Racket, which prints 64-bit floats
accurately (unlike Chicken, which depends on C to do it) returns
a value of 251.00000000000003.  The ceiling of that is indeed 252.0.

As Kernighan and Plauger said back in 1974:  "Floating point numbers
are like sandpiles:  every time you move one, you lose a little sand
and pick up a little dirt."  It's still true.

-- 
John Cowan          http://www.ccil.org/~cowan        address@hidden
Barry thirteen gules and argent on a canton azure fifty mullets of five
points of the second,  six, five, six, five, six, five, six, five, and six.
        --blazoning the U.S. flag