Check if a numeric series contains zero with a negative sign (-0)
or a positive sign (+0). See details.
Value
A single logical: whether -0 is a discrete value in the series
for has_negative_zero(), and whether +0 is a discrete value for
has_positive_zero(). Both can be TRUE; see details.
Details
While +0 and -0 are identical in R, they have a latent sign that
appears in reciprocals: 1 / +0 is Inf, while 1 / -0 is -Inf. The
has_negative_zero() and has_positive_zero() functions report whether
-0 and +0 are discrete values in the numeric series. Behaviour is
consistent with signed zero in numeric vectors.
A numeric series can contain both -0 and +0, like c(0, -0). Only one
zero is returned by next_discrete(), prev_discrete(), or
get_discretes_in(), as with unique(c(0, -0)). Their presence remains
latent and appears when the series is inverted, giving both Inf and
-Inf. See the examples.
Examples
has_negative_zero(integers())
#> [1] FALSE
has_positive_zero(integers())
#> [1] TRUE
# Integer 0 can never be negative, but double can:
has_negative_zero(-integers())
#> [1] FALSE
has_negative_zero(-1.5 * integers())
#> [1] TRUE
# -0 and +0 can co-exist, but are never double counted. However, they
# get expressed differently when the series is inverted.
a <- c(0, -0)
num_discretes(a)
#> [1] 1
num_discretes(1 / a)
#> [1] 2
b <- dsct_union(integers(from = -1, to = 1), -0)
num_discretes(b)
#> [1] 3
num_discretes(1 / b)
#> [1] 4