Advanced topics • loud

library(loud)
#> Loading required package: rlang
library(testthat)
#> 
#> Attaching package: 'testthat'
#> The following objects are masked from 'package:rlang':
#> 
#>     is_false, is_null, is_true

Monadic laws

First draft: are we dealing with a monad?

First law

a <- loud_value(10)

test_that("first monadic law", {
  expect_equal(flat_loudly(a, sqrt), sqrt(a$result))
})
#> Test passed 🎉

Second law

test_that("second monadic law", {
  expect_equal(flat_loudly(a, loud_value), a)
})
#> Test passed 😀

Third law

a <- loud_value(10)

loud_sqrt <- loudly(sqrt)
loud_exp <- loudly(exp)
loud_mean <- loudly(mean)

loud_exp_after_sqrt <- loudly(purrr::compose(exp, sqrt))

test_that("third monadic law", {
  expect_equal(
    (bind_loudly(a, loud_sqrt)) |>
      bind_loudly(loud_exp),
    a |>
      (\(x) bind_loudly(x, loud_sqrt) |> bind_loudly(loud_exp))()
  )
})
#> Test passed 🥳