In dtkaplan/checkr: Facilities for checking R submissions in tutorials

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

Arithmetic

Write a statement to calculate 2 plus 2.

right_1 <- for_checkr(quote(2 + 2))
right_2 <- for_checkr(quote(`+`(2, 2)))
wrong_1 <- for_checkr(quote(2 * 2))
wrong_2 <- for_checkr(quote(3 + 1))
wrong_3 <- for_checkr(quote(2 + 5))

ex <- wrong_3 
check_binding(
    ex, 
    {..(val); .(fn)(.(a), .(b))},
    insist(fn %same_as% `+`,
           "\"Plus\" means addition, not {{fn}}."),
    insist(a == 2 && b == 2, "We said, 'add **two plus two**, not {{a}} + {{b}}."),
    passif(val == 4, "Good job!")
)

Trigonometry

What is the x-coordinate of a point on the unit circle at π/2?

right_1 <- for_checkr(quote(cos(pi / 2)))
wrong_1 <- for_checkr(quote(sin(pi / 2))) # using wrong trig function
wrong_2 <- for_checkr(quote(cos(90))) # using degrees
wrong_3 <- for_checkr(quote(cos(pi))) # wrong value
wrong_4 <- for_checkr(quote(cos(pi, 2))) # wrong calling syntax
wrong_5 <- for_checkr(quote(cos(3.14 / 2))) # bad approximation

# same tests to be run on each of the examples
tests <- function(ex) { 
  t1 <- misconception(ex, line_calling(ex, sin), "Sorry. We're asking for the **x** coordinate, not the y coordinate.")
  if (failed(t1)) return(t1)
  t1 <- check_binding(ex, cos(pi / 2), 
           passif(TRUE, 
              "Exactly! Nice use of name 'pi' to represent π.")) 
  if (passed(t1)) return(t1)
  check_binding(ex, {..(val); .(fn)(.(arg))},
         insist(fn %same_as% `cos`, "{{fn}} is not the correct trigonometric function."),
         # Specific misconceptions
         failif(arg %same_as% pi, "The angle should be π/2, not π."),
         failif(arg == 90, "True, pi/2 is the same as 90 degrees. But specify the angle in radians, not degrees."),
         insist("pi" %in% all.names(arg), "Please use the symbolic `pi`.")
    )
}

tests(right_1)
tests(wrong_1)
tests(wrong_2)
tests(wrong_3)
tests(wrong_4)
tests(wrong_5)

dtkaplan/checkr documentation built on May 15, 2019, 4:59 p.m.