[plt-scheme] typed scheme intro

Two complex dimentions. :)

On Thu, Apr 8, 2010 at 3:25 PM, Sam Tobin-Hochstadt <samth at ccs.neu.edu> wrote:
> On Thu, Apr 8, 2010 at 4:21 PM, Robby Findler
> <robby at eecs.northwestern.edu> wrote:
>> Ah. I see. (I didn't understand the error message, fwiw. I do now that
>> I know what the error is, tho... kind of.)
>>
>> I changed the fields to Number and it also type checked. Maybe that's
>> also a good change to the example?
>
> I didn't really want them to be 4D points, but given that positiveness
> isn't represented in the type system, maybe I should change them.  Or
> add a NonNegativeReal type.  Or maybe we should have `real-sqrt'.
>
>>
>> Robby
>>
>> On Thu, Apr 8, 2010 at 3:17 PM, Sam Tobin-Hochstadt <samth at ccs.neu.edu> wrote:
>>> On Thu, Apr 8, 2010 at 4:15 PM, Robby Findler
>>> <robby at eecs.northwestern.edu> wrote:
>>>> What type annotations did you put, exactly? I tried changing the
>>>> result of mag to Number and otherwise leaving it as is (from the docs)
>>>> and I get this:
>>>>
>>>> Welcome to DrScheme, version 4.2.5.6-svn8apr2010 [3m].
>>>> Language: typed/scheme; memory limit: 512 MB.
>>>> . Type Checker: No function domains matched in function application:
>>>> Domains: Exact-Nonnegative-Integer
>>>>         Number
>>>> Arguments: Number Number
>>>>  in: (sqrt (sqr (pt-x p)) (sqr (pt-y p)))
>>>
>>> That's from the missing `+' operation.
>>> --
>>> sam th
>>> samth at ccs.neu.edu
>>>
>>
>
>
>
> --
> sam th
> samth at ccs.neu.edu
>