更新R表达式

我想交换一些用户编写的代码。我不知道如何更新这些表情。我可以 append() ,但不是 replace()

orig_code <-
  parse(text = 
    "library(tidyverse)   
    list_1 <- list(a = 1, b = 2)"
  )

new_code <- parse(text = "list_1 <- list(a = 1:3)")


# I can append
append(
  x = orig_code,
  values = new_code
)
#> expression(
#>   library(tidyverse), 
#>   list_1 <- list(a = 1, b = 2), 
#>   list_1 <- list(a = 1:3)
#> )


# but not replace
replace(
  x = orig_code,
  list = 2,
  values = new_code
)
#> expression(
#>   library(tidyverse), 
#>   list_1 <- list(a = 1, b = 2)
#> )

# or reassign
orig_code[[2]] <- new_code

orig_code
#> expression(
#>   library(tidyverse), 
#>   list_1 <- list(a = 1, b = 2)
#> )

^{创建于2020-07-05 reprex package}