Check whether the student defined a function correctly

check_fun_def checks whether an object is defined in the student enviornment, and returns a state that can be piped to:

• check_arguments, to check whether the correct arguments where specified.

• check_call, to call the function with the provided arguments, and produces a state that can be piped to check_output, check_result and check_error to compare the output, result or error from calling the function between student and solution.

• check_body, that returns a state that focuses on the body that defines the function. Note that you cannot use check_object to compare variables that are limited to the function scope.

check_fun_def(state, name, undefined_msg = NULL, no_fundef_msg = NULL,
  append = TRUE)

check_arguments(state, incorrect_number_arguments_msg = NULL,
  append = TRUE)

# S3 method for FunDefState
check_body(state, not_found_msg = NULL,
  append = TRUE, ...)

check_call(state, ...)

Arguments

state	the state to start from
name	The name of the function to test
undefined_msg	Custom message in case the specified function was not defined
no_fundef_msg	Custom message in case the function specified in name is not a function.
append	Whether or not to append the feedback to feedback built in previous states
incorrect_number_arguments_msg	Optional feedback message in case the function does not have the correct number of arguments.
not_found_msg	Custom feedback message if function definition was not found.
...	arguments to pass to the user-defined function to test result, output or error in a later stage

Examples

if (FALSE) {
# Example:
my_op <- function(a, b) {
  stopifnot(length(a) == length(b))
  return(abs(a) + abs(b))
}

# Robust SCT
ex() %>% check_fun_def('my_op') %>% check_correct(
  {
    check_call(., c(1, 2), c(3, 4)) %>% check_result() %>% check_equal()
    check_call(., c(1, -2), c(3, -4)) %>% check_result() %>% check_equal()
    check_call(., c(-1, 2), c(-3, 4)) %>% check_result() %>% check_equal()
    check_call(., 1, c(3, 4)) %>% check_error()
    check_call(., c(1, -2), 3) %>% check_error()
  },
  {
    check_arguments(.)
    check_body(.) %>% {
      check_function(., 'stopifnot') %>% check_arg('...') %>% {
        check_function(., 'length', index = 1) %>% check_arg('x') %>% check_equal(eval = FALSE)
        check_function(., 'length', index = 2) %>% check_arg('x') %>% check_equal(eval = FALSE)
        check_code(., '==')
      }
      check_function(., 'abs', index = 1) %>% check_arg('x') %>% check_equal(eval = FALSE)
      check_function(., 'abs', index = 2) %>% check_arg('x') %>% check_equal(eval = FALSE)
    }
  }
)
}