Why do I need quosures?

User environment:

div100 <- function(x) {
  x / 100
}

dplyr::starwars %>%
  foo::summarise_bmi(mass, div100(height))

Package foo:

bmi <- function(mass, height) {
  mass / height^2
}

summarise_bmi <- function(data, mass, height) {
  data %>%
    bar::summarise_stats(bmi({{ mass }}, {{ height }}))
}

Package bar:

check_numeric <- function(x) {
  stopifnot(is.numeric(x))
  x
}

summarise_stats <- function(data, var) {
  data %>%
    dplyr::transmute(
      var = check_numeric({{ var }})
    ) %>%
    dplyr::summarise(
      mean = mean(var, na.rm = TRUE),
      sd = sd(var, na.rm = TRUE)
    )
}

All add up to…

dplyr::transmute(
var =
  check_numeric(
    bmi(
      mass,
      div100(height)
    )
  )
)

With each tab over indicating a quosure boundary

• You need to make sure that mass and height stay properly tracked throughout environments