[plt-scheme] The perfect teaching language--Is this too much to ask for?

"working on" in the very loosest sense of the world. :)

Robby

On Sat, Jun 13, 2009 at 6:36 PM, Matthias Felleisen
<matthias at ccs.neu.edu> wrote:
>
> On Jun 13, 2009, at 7:04 PM, Todd O'Bryan wrote:
>
>> or am I still not correctly verbalizing/understanding what I'm asking for?
>
> You are but like a typical consumer and many computer scientists, you are
> proposing a solution instead of stating and describing the problem.
>
> ;; ---
>
> 1. We made the decision to go without static types for good reason. You
> don't want types (at the beginning).
>
> 2. What we call contracts in BSL and what we call contracts in PLT Scheme is
> only loosely related. So you don't want contracts either.
>
> 3. In the German version of HtDP, dubbed DeinProgram, you state HtDP-style
> contracts in a formal language and they are checked as your BSL/ISL programs
> are run. It would cut down your students' 'debugging' time a lot. See
> DeinProgram in DrScheme, but you may need to know a bit of German.
>
> 4. We intend to support something like this sooner or later. Robby has been
> working on this since 2004.
>
> 5. I don't understand how your students can have test cases for each
> function and NOT see that their functions are producing the wrong things.
> Code excerpts would be helpful.
>
> All in all you aren't asking for a perfect language. You're asking for very
> doable things. (Python's nonsense confused the heck out of you. Give up on
> it. Study ML and then jump to Cayenne. Students will never mistakes again,
> because they won't get any programs past the type checkers :-)
>
> -- Matthias
>
>
> ;; ----
>
>
> P.S. For your reading pleasure, a first draft of the proposed teachpack for
> providing type-of and friends:
>
> #lang scheme
>
> (require lang/prim)
>
> (provide type-of)
>
> ;; Any -> Type
> (define (type-of a)
>  (cond
>    [(number? a) Number]
>    [(string? a) String]
>    [(boolean? a) Boolean]
>    [(procedure? a) Procedure]
>    [(type? a) Type]))
>
> (define-syntax-rule (def-types type? Name ...)
>  (begin (provide type? Name ...)
>         (define (type? x)
>           (member x (list Name ...)))
>         (define Name (gensym 'Name))
>         ...))
>
> (def-types type? Type Number String Boolean Procedure)
>
>
> I took the liberty of writing a macro to define the types. You can define
> them one by one, w/i the BSL language!!!
>
> Here is an interaction:
>
> Welcome to DrScheme, version 4.2.0.3-svn12jun2009 [3m].
> Language: Intermediate Student.
> This program should be tested.
>> (type-of 3)
> 'Number3989
>> (type-of cons)
> 'Procedure3992
>> (type-of true)
> 'Boolean3991
>> (type-of (type-of true))
> 'Type3988
>>
>
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