methods (version 3.5.3)

hasArg: Look for an Argument in the Call

Description

Returns TRUE if name corresponds to an argument in the call, either a formal argument to the function, or a component of ..., and FALSE otherwise.

Usage

hasArg(name)

Arguments

name

The name of a potential argument, as an unquoted name or character string.

Value

Always TRUE or FALSE as described above.

Details

The expression hasArg(x), for example, is similar to !missing(x), with two exceptions. First, hasArg will look for an argument named x in the call if x is not a formal argument to the calling function, but ... is. Second, hasArg never generates an error if given a name as an argument, whereas missing(x) generates an error if x is not a formal argument.

See Also

missing

Examples

# NOT RUN {
ftest <- function(x1, ...) c(hasArg(x1), hasArg("y2"))

ftest(1) ## c(TRUE, FALSE)
ftest(1, 2)  ## c(TRUE, FALSE)
ftest(y2 = 2)   ## c(FALSE, TRUE)
ftest(y = 2)    ## c(FALSE, FALSE) (no partial matching)
ftest(y2 = 2, x = 1)  ## c(TRUE, TRUE) partial match x1
# }