Creating functions example

• rlang::new_function() creates a function from its three components and supports tidy evaluation

• Alternative to function factories.

Example:

power <- function(exponent) {
  new_function(
    exprs(x = ), 
    expr({
      x ^ !!exponent
    }), 
    caller_env()
  )
}
power(0.5)
#> function (x) 
#> {
#>     x^0.5
#> }

Another example, is graphics::curve that allows you to plot an expression without creating a function. It could be implemented like this:

curve2 <- function(expr, xlim = c(0, 1), n = 100) {
  expr <- enexpr(expr)
  f <- new_function(exprs(x = ), expr)
  
  x <- seq(xlim[1], xlim[2], length = n)
  y <- f(x)

  plot(x, y, type = "l", ylab = expr_text(expr))
}
curve2(sin(exp(4 * x)), n = 1000)