I have removed the signatures from BSL precisely for reasons like that. Please update to Version 5.0.2.
Once again, apologies for allowing checked signatures to slip into 5.0.1. -- Matthias On Nov 19, 2010, at 12:57 PM, Don Blaheta wrote: > A student of mine is having trouble keeping track of when to use capital > vs lowercase letters---a common problem I've seen before, with any intro > language---and in particular, keeps trying to write True and False > instead of true and false. After a very strange discussion with him I > went and tested some things and was flabbergasted to discover that True > actually was a defined name of which the value is opaque and the error > messages deeply mysterious. > > I get that you guys are working on Typed Racket, and I get that you > think that adding all this extra syntax into tlfka Scheme will improve > it. But I can't believe that anyone thought it would be a good idea to > expose this in BSL. > > This isn't just a strange choice, it runs *precisely counter* to the > *main stated goal* of the teaching languages, to exclude from the > language anything that the students might accidentally type, that would > be valid in the full language but was "not what they meant" and not > something that they yet knew to avoid. > > This one is especially insidious because the mostly opaque value of True > and False gets printed as "(make-signature ...)" which, since we *have* > talked about function signatures, seems to make reference to some other > concept which is a total red herring wrt the actual problem (at least as > far as they're concerned). Consider the simple BSL program: > > ;; >5 : num -> boolean > ; determines whether a given number is greater than 5 > (define (>5 n) > (> n 5)) > (check-expect (>5 3) False) > (check-expect (>5 7) True) > > This yields the test case failures: > > Actual value false differs from (make-signature ...), the expected > value. > at line 4, column 0 > Actual value true differs from (make-signature ...), the expected value. > at line 5, column 0 > > I nearly filed this as a bug, and I still claim that it is one, but once > I figured out what was actually going on (and the TR connection) I > figured I'd best post it here. > > -- > -=-Don blaheta-=-dblah...@monm.edu-=-=-<http://www.monmsci.net/~dblaheta/>-=- > A diva who specializes in risqué arias is an off-coloratura soprano. > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
