makeCaseWhen

call <- substitute(ifelse(v == 1,
                          "banana",
                          ifelse(v == 2,
                                 2,
                                 NA))
)

parse_ifelse <- function(call) {
  if (deparse(call[[3]][[1]]) == "ifelse") {
    top_call <- deparse(call[[2]])
    return(
      paste0(top_call, " & ",
                  parse_ifelse(call[[3]]))
    )
  }

  top_call <- paste0(deparse(call[[2]]), " ~ ", deparse(call[[3]]))

  if (deparse(call[[4]][[1]]) == "ifelse") {
    return(c(top_call,
             parse_ifelse(call[[4]])))
  }
  return(paste0(deparse(call[[2]]), " ~ ", deparse(call[[3]])))
}

getTerminalCase <- function(call) {
  if (deparse(call[[4]][[1]]) == "ifelse") {
    return(getTerminalCase(call[[4]]))
  } else {
    return(paste0( "TRUE ~ ", deparse(call[[4]])))
  }
}

makeCaseWhen <- function(call) {
  cases <- c(
    parse_ifelse(call),
    getTerminalCase(call)
  )
  out <- c(
    "dplyr::case_when(",
    paste0(cases, collapse = ",\n"),
    ")"
  )
  paste0(out, collapse = "\n")
}
cat(makeCaseWhen(call))

This was a great Saturday morning coffee challenge! No judgement, just having fun with rlang:

library(rlang)

cases <- function(x) {
  if (is_call(x, "ifelse")) {
    test <- x[[2]]
    if_true <- x[[3]]
    if_false <- x[[4]]
    
    c(
      call2("~", test, if_true),
      cases(if_false)
    )
  } else {
    list(call2("~", TRUE, x))
  }
}

x <- expr(ifelse(a == 12, "twelve", ifelse(a == 13, "thirteen", "not twelve or 13")))
call2("case_when", !!!cases(x))
#> case_when(a == 12 ~ "twelve", a == 13 ~ "thirteen", TRUE ~ "not twelve or 13")

^{Created on 2019-10-26 by the reprex package (v0.2.1)}

Awesome!

…

On Sat., Oct. 26, 2019, 11:39 a.m. Dewey Dunnington, < ***@***.***> wrote: This was a great Saturday morning coffee challenge! No judgement, just having fun with rlang: library(rlang) cases <- function(x, cases = list()) { if (is_call(x, "ifelse")) { test <- x[[2]] if_true <- x[[3]] if_false <- x[[4]] c( cases, call2("~", test, if_true), cases(if_false) ) } else { list(call2("~", TRUE, x)) } } x <- expr(ifelse(a == 12, "twelve", ifelse(a == 13, "thirteen", "not twelve or 13"))) call2("case_when", !!!cases(x))#> case_when(a == 12 ~ "twelve", a == 13 ~ "thirteen", TRUE ~ "not twelve or 13") Created on 2019-10-26 by the reprex package <https://reprex.tidyverse.org> (v0.2.1) — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://gist.github.com/5b1c84e441e40675581c6d3e75ea0d0b?email_source=notifications&email_token=ACAG7FDTTVEATX545DMR2XTQQRJDVA5CNFSM4JFNQN62YY3PNVWWK3TUL52HS4DFVNDWS43UINXW23LFNZ2KUY3PNVWWK3TUL5UWJTQAF3FMK#gistcomment-3066565>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACAG7FBL2KAAS2ZTOSLSWETQQRJDVANCNFSM4JFNQN6Q> .