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  3. Intermediate Functional Programming with purrr

Exercise

Purrrfecting our function

We are still perfecting our function to detect if a list of URLs contains elements that are not available.

Let's review what we have coded so far:

  • An error extractor, by combining safely() and map(.x, "error").
  • A "non-null" extractor, by combining safely() and discard(.x, is.null).
  • A 404 generator, by using possibly(.x, otherwise = 404), which was turned into a function.

We'll change the behavior of this function a bit: you now want to be able to choose between returning either the results or the errors.

This will allow you to answer two questions with just one function: which are the unreachable URLs, and which are the reachable ones? To do this, you'll add a parameter called "type" inside this function.

The urls vector and safe_read() are available in your workspace.

Instructions

100 XP

Complete the function definition.

  • Map safe_read() to the list of URLs.
  • Set the names of the result to the list of URLs.
  • Transpose the result into a list of $result and $error.
  • Use pluck() to extract the type element.