discretes (version 0.1.0)

has_negative_zero: Check if a numeric series has a signed zero

Description

Check if a numeric series contains zero with a negative sign (-0) or a positive sign (+0). See details.

Usage

has_negative_zero(x)
has_positive_zero(x)

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.

Arguments

x

Numeric series (numeric vector or object of class "discretes").

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())
has_positive_zero(integers())

# Integer 0 can never be negative, but double can:
has_negative_zero(-integers())
has_negative_zero(-1.5 * integers())

# -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)
num_discretes(1 / a)

b <- dsct_union(integers(from = -1, to = 1), -0)
num_discretes(b)
num_discretes(1 / b)