[Rd] replicate evaluates its second argument in wrong environment

[Hadley Wickham]

This is a nice example of the motivation for tidy evaluation — since
enquo() captures the environment in which the promise should be
evaluated, there's no need for an additional explicit argument.

library(rlang)

replicate2 <- function (n, expr, simplify = "array") {
  exnr <- enquo(expr)
  sapply(integer(n), function(i) eval_tidy(expr), simplify = simplify)
}

doRep2 <- function(a, b) sapply(a, replicate2, b)
doRep2(3, 2)
#>      [,1]
#> [1,]    2
#> [2,]    2
#> [3,]    2

Hadley

On Sat, Feb 13, 2021 at 7:09 AM Gabor Grothendieck
<ggrothendieck using gmail.com> wrote:
>
> Currently replicate used within sapply within a function can fail
> because it gets the environment for its second argument, which is
> currently hard coded to be the parent frame, wrong.  See this link for
> a full example of how it goes wrong and how it could be made to work
> if it were possible to pass an envir argument to it.
>
> https://stackoverflow.com/questions/66184446/sapplya-replicate-b-expression-no-longer-works-inside-a-function/66185079#66185079
>
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