list? is not available [1] in either BSL or BSL with list abbreviations. Why? Lists are used everywhere even in BSL, and `list?` literally appears in half its documented contracts in beginner docs [2] — how should students understand them?
I've looked for reasons, to no avail. I've only learned that: - unlike in Racket, the disjunction of `cons?` and `empty?` would be enough to redefine `list?`, since improper lists are forbidden - HtDP/2e doesn't mention `list?` in the chapter on lists [3], even though it comes after the chapter where "sum types" (ahem, itemizations) are introduced. [1] Racket rejects `(list? empty)` with "list?: this function is not defined" [2] http://docs.racket-lang.org/htdp-langs/beginner.html [3] http://www.ccs.neu.edu/home/matthias/HtDP2e/Draft/part_two.html [4] http://www.ccs.neu.edu/home/matthias/HtDP2e/Draft/part_one.html -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
