Hi All, we have discovered that in 6.4 DrRacket (Advanced Student) seems to have a bug generating error messages for foldl/foldr:
(foldl + (list 2 3 4) 0) gives an error message "foldl: 2th argument must be a list, given 0" (in addition to the incorrect "th" for "2nd", the 0 is actually the third argument, not second). There is also a somewhat misleading error (for beginners) in 6.4 and earlier versions, shown with a somewhat artificial example: (map (lambda (x y) (+ x y)) (list 2 3 4)) gives and error: the given procedure's expected number of arguments does not match the given number of lists given procedure: #<procedure> expected: 2 given: 1 This is technically correct, but not understandable to a student since most likely they mistakenly used a two-argument function instead of a one-argument one. In fact, students are never shown a map with multiple lists. A better message would say that a one-argument function was expected, but a two-argument function was given. The second error is somewhat of a design choice, but the first one (with foldl) is a bug. If there is a way to patch it in 6.4, that would be greatly appreciated. Cheers, Elena -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
