dipsaus (version 0.1.6)

get_dots: Get element from dots '...'

Description

Get specific key values from '...' without evaluating the rest of arguments.

Usage

get_dots(..name, ..default = NULL, ...)

Arguments

..name

character name of the argument

..default

R object to return if argument not found

...

dots that contains argument

Details

One could use list(...)[[name]] to extract any keys from the dots. However, such way reduces code readability. If some arguments have not evaluated, list(...) will force evaluating them. Normally it's fine if these expressions take little time to run, but if the expression require time to run, get_dots avoids unnecessary evaluations.

Examples

# NOT RUN {

# ------------------------ Basic Usage ---------------------------
plot2 <- function(...){
  title = get_dots('main', 'There is no title', ...)
  plot(...)
  title
}

plot2(1:10)
plot2(1:10, main = 'Scatter Plot of 1:10')

# ------------------------ Comparisons ----------------------------
f1 <- function(...){ get_dots('x', ...) }
f2 <- function(...){ list(...)[['x']] }
delayedAssign('y', { cat('y is evaluated!') })

# y will not evaluate
f1(x = 1, y = y)

# y gets evaluated
f2(x = 1, y = y)

# -------------------- Decorator example --------------------------
ret_range <- function(which_range = 'y'){
  function(f){
    function(...){
      f(...)
      y_range <- range(get_dots(which_range, 0, ...))
      y_range
    }
  }
}
plot_ret_yrange <- plot %D% ret_range('y')
plot_ret_yrange(x = 1:10, y = rnorm(10))


# }