unknown() creates an expression used to signify that the value will be specified at a later time.

## Usage

unknown()

is_unknown(x)

has_unknowns(object)

## Arguments

x

An object or vector or objects to test for unknown-ness.

object

An object of class param.

## Value

unknown() returns expression value for unknown().

is_unknown() returns a vector of logicals as long as x that are TRUE

is the element of x is unknown, and FALSE otherwise.

has_unknowns() returns a single logical indicating if the range of a param

object has any unknown values.

## Examples


# Just returns an expression
unknown()
#> unknown()

# Of course, true!
is_unknown(unknown())
#> [1] TRUE

# Create a range with a minimum of 1
# and an unknown maximum
range <- c(1, unknown())

range
#> [[1]]
#> [1] 1
#>
#> [[2]]
#> unknown()
#>

# The first value is known, the
# second is not
is_unknown(range)
#> [1] FALSE  TRUE

# mtry()'s maximum value is not known at
# creation time
has_unknowns(mtry())
#> [1] TRUE