| % File src/library/base/man/args.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2007, 2015 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{args} |
| \alias{args} |
| \title{Argument List of a Function} |
| \description{ |
| Displays the argument names and corresponding default values of a |
| function or primitive. |
| } |
| \usage{ |
| args(name) |
| } |
| \arguments{ |
| \item{name}{a function (a closure or a primitive). |
| If \code{name} is a character string then the function with that |
| name is found and used.} |
| } |
| \value{ |
| For a closure, a closure with identical formal argument list but an |
| empty (\code{NULL}) body. |
| |
| For a primitive, a closure with the documented usage and \code{NULL} |
| body. Note that some primitives do not make use of named arguments |
| and match by position rather than name. |
| |
| \code{NULL} in case of a non-function. |
| } |
| \details{ |
| This function is mainly used interactively to print the argument list |
| of a function. For programming, consider using \code{\link{formals}} |
| instead. |
| } |
| \references{ |
| Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) |
| \emph{The New S Language}. |
| Wadsworth & Brooks/Cole. |
| } |
| \seealso{ |
| \code{\link{formals}}, \code{\link{help}}; |
| \code{\link{str}} also prints the argument list of a function. |
| } |
| \examples{ |
| ## "regular" (non-primitive) functions "print their arguments" |
| ## (by returning another function with NULL body which you also see): |
| args(ls) |
| args(graphics::plot.default) |
| utils::str(ls) # (just "prints": does not show a NULL) |
| |
| ## You can also pass a string naming a function. |
| args("scan") |
| ## ...but :: package specification doesn't work in this case. |
| tryCatch(args("graphics::plot.default"), error = print) |
| |
| ## As explained above, args() gives a function with empty body: |
| list(is.f = is.function(args(scan)), body = body(args(scan))) |
| |
| ## Primitive functions mostly behave like non-primitive functions. |
| args(c) |
| args(`+`) |
| ## primitive functions without well-defined argument list return NULL: |
| args(`if`) |
| } |
| \keyword{documentation} |