The Sifflet visual functional programming language and aid to understanding recursive functions (http://mypage.iu.edu/~gdweber/software/sifflet/home.html)

#15Unbound variable []

15 In the test function list_of_2, evaluating [] results in "error: unbound variable: []". Ditto repeat_a_b. O: 2010 aug 16 P: high C: 2010 aug 16 -- fixed.