At Fri, 01 Mar 2013 09:05:21 +0100, Marijn wrote: > On 27-02-13 21:51, Neil Toronto wrote: > > > (An example that came up in the implementation of matrix norms: the > > type of (sqrt (/ 1 x)) isn't Nonnegative-Real if x : > > Nonnegative-Real, but Complex. Consider x = -0.0. Without TR's > > complaints, `matrix-norm' would have contained a time bomb.) > > Should -0.0 really be a Nonnegative-Real?
That's by design. Including both floating-point zeroes in both non-negative and non-positive types is necessary to make occurrence typing useful for comparisons between floating-point numbers and zero (see PR12706 for more details). It also simplifies parts of the numeric base environment significantly. Vincent _________________________ Racket Developers list: http://lists.racket-lang.org/dev
