How to find the function arguments of a function within a given environment?

Question

I am trying to build a data frame like,

  fun     args               uses_arg              
1 myfun   function (x, w=1)  function (x, arg)

where column "fun" contains all the functions in the chosen environment, and args the function arguments. I would like to have the info in a dataframe for further filtering. Consider the following code.

myfun <- function(x, w=1) return(x * w)
 lsf.str()
# myfun : function (x, w)               # info from lsf.str().
# uses_arg : function (x, arg) 

 lsf_text <- lsf.str()
 class(lsf_text)
#  [1] "ls_str"                         # class.
#
 print.default(lsf_text)                # print as is.
#  [1] "myfun"
#  attr(,"envir")
#  <environment: R_GlobalEnv>
#  attr(,"mode")
#  [1] "function"
#
# print class 
 print(lsf_text)
#  myfun : function (x, w)     # <<<<<<<<<<<
#  uses_arg : function (x, arg)# <<<<<<<<<<< 
#-------------------------------------------

• Q1: How or where can I find the function call after the semicolon, i.e. "function (x, w)", preferably using R base functions.
• Q2: Where to find the actual print function used. The function could give a clue.

Answer 1

You could do sth like

> fnm <- lsf.str()
> res <- list(fun=as.list(fnm[seq_along(fnm)]), 
+      args=lapply(fnm, \(x) names(formals(get(x, .GlobalEnv)))),
+      param=lapply(fnm, \(x) gsub(r'{.*(?<=\()(.*)(?=\)).*}', '\\1', 
+                                  deparse(args(get(x, .GlobalEnv)))[[1]],
+                                  perl=TRUE) |> strsplit(', '))) |>
+   list2DF()
> res
     fun    args    param
1 myfun1    x, w x, w = 1
2 myfun2 x, z, w  x, z, w

where

> str(res)
'data.frame':   2 obs. of  3 variables:
 $ fun  :List of 2
  ..$ : chr "myfun1"
  ..$ : chr "myfun2"
 $ args :List of 2
  ..$ : chr  "x" "w"
  ..$ : chr  "x" "z" "w"
 $ param:List of 2
  ..$ :List of 1
  .. ..$ : chr  "x" "w = 1"
  ..$ :List of 1
  .. ..$ : chr  "x" "z" "w"

Note, that there's a utils:::print.ls_str.

---

Data:

myfun1 <- function(x, w=1) return(x * w)
myfun2 <- function(x, z, w) return(z*(x / w))