| body {base} | R Documentation |
Access to and Manipulation of the Body of a Function
Description
Get or set the body of a function which is basically all of
the function definition but its formal arguments (formals),
see the ‘Details’.
Usage
body(fun = sys.function(sys.parent()))
body(fun, envir = environment(fun)) <- value
Arguments
fun |
a function object, or see ‘Details’. |
envir |
environment in which the function should be defined. |
value |
an object, usually a language object: see section ‘Value’. |
Details
For the first form, fun can be a character string
naming the function to be manipulated, which is searched for from the
parent frame. If it is not specified, the function calling
body is used.
The bodies of all but the simplest are braced expressions, that is
calls to {: see the ‘Examples’ section for how to
create such a call.
Value
body returns the body of the function specified. This is
normally a language object, most often a call to {, but
it can also be a symbol such as pi or a constant
(e.g., 3 or "R") to be the return value of the function.
The replacement form sets the body of a function to the
object on the right hand side, and (potentially) resets the
environment of the function, and drops
attributes. If value is of class
"expression" the first element is used as the body: any
additional elements are ignored, with a warning.
See Also
The three parts of a (non-primitive) function are its
formals, body, and environment.
Further, see
alist,
args,
function.
Examples
body(body)
f <- function(x) x^5
body(f) <- quote(5^x)
## or equivalently body(f) <- expression(5^x)
f(3) # = 125
body(f)
## creating a multi-expression body
e <- expression(y <- x^2, return(y)) # or a list
body(f) <- as.call(c(as.name("{"), e))
f
f(8)
## Using substitute() may be simpler than 'as.call(c(as.name("{",..)))':
stopifnot(identical(body(f), substitute({ y <- x^2; return(y) })))