strb.R

library(purrr)
library(assertthat)

let <- function(...) quos(...)
`:=` <- function(left, right){
  names <- map_chr(left, quo_name)
  assert_that( length(right) >= length(names) )
  env <- parent.frame()
  
  for( i in seq_along(names) ){
    assign( names[i], right[[i]], envir = env)
  }
  invisible(NULL)
}

x <- rnorm(100)
let(low,up) := range(x)


# alternatively
library(purrr)
library(assertthat)

tie <- structure( NA, class = "tie_proxy")

`[<-.tie_proxy` <- function(x, ..., value){
  dots <- quos(...)
  assert_that( length(value) >= length(dots) )
  env <- parent.frame()
  
  for( i in seq_along(names) ){
    dot <- dots[[i]]
    if( !quo_is_missing(dot) ){
      assign( quo_name(dot), value[[i]], envir = env)
    } 
  }
  invisible(x)
}
x <- rnorm(100)
tie[low,up] <- range(x)

> x <- rnorm(100)
> let(low,up) := range(x)
> low
[1] -2.327442
> up
[1] 2.273341

> let[,q25,q50,q75,q100] = quantile(x)
> q25
[1] -0.5364728
> q75
[1] 0.8586446

It is a pity that just defining let<- is not possible.

Yeah that was the first thing I tried. 😞