The R Project SVN R

## Tests for various features of IEC60559 doubles.
## Most of these are optional, so this is a sloppy test.

# Goes to denormal (aka subnormal) numbers at -708.4
exp(c(-745:-740, -730, -720, -710:-705))

# goes to subnormal numbers at -308, to zero at ca 5e-324.
10^-(324:307)
2^-(1022:1075)

# And because most libm pow() functions special-case integer powers.
10^-(324:307-0.01)/10^0.01

# IEC60559 mandates this, but C99/C11 do not.
# Mingw-w64 did not do so in v 2.0.1
(x <- 0*(-1)) # negative zero (prints as '0' in R on purpose!)
rt_0 <- sqrt(x) # ditto  -- but sprintf() shows "-0" :
sprintf("%g, rt = %g, .^2 = %g", x, sqrt(x), x^2)
stopifnot(exprs = {
    identical(1/ x, -Inf)
    identical(1/-x, +Inf)
    identical(x, -x,) # default num.eq=TRUE  ==> -0 "identical" 0
    ! identical(x, -x,    num.eq=FALSE) # but not bitwise identical
    identical(x, sqrt(x), num.eq=FALSE) # sqrt(-0) == -0
    identical(-x, x^2,    num.eq=FALSE) # (-0)^2   == +0 = --0
})