#  File src/library/base/R/formals.R
#  Part of the R package, https://www.R-project.org
#
#  Copyright (C) 1995-2023 The R Core Team
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
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formals <- function(fun = sys.function(sys.parent()), envir = parent.frame()) {
    if(is.character(fun))
	fun <- get(fun, mode = "function", envir = envir)
    .Internal(formals(fun))
}

body <- function(fun = sys.function(sys.parent())) {
    if(is.character(fun))
	fun <- get(fun, mode = "function", envir = parent.frame())
    .Internal(body(fun))
}

alist <- function (...) as.list(sys.call())[-1L]

`body<-` <- function (fun, envir = environment(fun), value) {
    if(!is.function(fun)) warning("'fun' is not a function") # TODO[2017]: stop()
    if (is.expression(value)) {
        if (length(value) > 1L)
            warning("using the first element of 'value' of type \"expression\"")
        value <- value[[1L]]
    }
    as.function(c(formals(fun), 
                  if(is.null(value) || is.atomic(value) || is.list(value)) list(value) else value),
                envir)
}

`formals<-` <- function (fun, envir = environment(fun), value)
{
    if(!is.function(fun)) warning("'fun' is not a function") # TODO[2017]: stop()
    bd <- body(fun)
    as.function(c(value,
                  ## is.null(.)  || is.atomic(.) checking for _constant_ :
                  if(is.null(bd) || is.atomic(bd) || is.list(bd)) list(bd) else bd),
                envir)
}
