match.fun {base} | R Documentation |
This function is called inside functions that take a function as argument. It's purpose is to extract the desired function object while avoiding undesired matching to objects of other types.
match.fun(FUN, descend = TRUE)
FUN |
item to match as function. |
descend |
logical; control whether to search past non-function objects. |
match.fun
is not intended to be used at the top level
since it will perform matching in the parent of the caller.
It is assumed that FUN
is an argument passed to the caller and is
a function or a character string containing the name of a function.
Returns an error if no matching function is found.
A function matching FUN
or an error is generated.
The descend
argument is a bit of misnomer and probably not
actually needed by anything. It may go away in the future.
It is impossible to fully foolproof this. If one attach
es a
list or data frame containing a character object with the same name
of a system function, it will be used.
Peter Dalgaard and Robert Gentleman, based on an earlier version by Jonathan Rougier
# Same as get("*"): match.fun("*") # Overwrite outer with a vector outer <- 1:5 match.fun(outer, descend = FALSE) #-> Error: not a function match.fun(outer) # finds it anyway is.function(match.fun("outer")) # as well