check.expr: Test: Compare the expression check.expr evaluated in the...
In skranz/RTutor2: Complete rewrite of RTutor internals combined with armd

Test: Compare the expression check.expr evaluated in the student's environment with the solution correct.expr

check.expr(check.expr, correct.expr,
  failure.message = "{{check_expr}} has the wrong values!",
  success.message = "Great, {{check_expr}} seems correct.", part = NULL,
  ps = get.ps(), stud.env = ps$stud.env, verbose = FALSE,
  unsubst.check.expr = NULL, unsubst.correct.expr = NULL,
  str.check.expr = NULL, str.correct.expr = NULL,
  tol = .Machine$double.eps^0.5)

`check.expr`	the expression to be checked
`correct.expr`	the correct expression
`vars`	a variable name or vector of variable names
`exists`	shall existence be checked (similar length, class, values)
`failure.exists`	a message that is shown if the variable does not exists (similar the other failure.??? variables)
`failure.message.add`	a text that will be added to all failure messages