Both Clojure and Rust are not very fast to learn to the problem-solving level. Other languages like Java or C++ can substitute for them. APL probably too hard to learn in 1-day
I'm convinced a moderately intelligent person with good grasp of high school mathematics can learn the entire core of APL in 24 hours of study (which of course is more than 1 day) with appropriate tutoring. Lack of programming experience is a plus.
Yes, I'm willing to tutor a student to test my claim.
