[racket] TR Keyword Args (Lil Help)

From: Ray Racine (ray.racine at gmail.com)
Date: Fri Aug 10 15:34:17 EDT 2012

Sure, I'll probably sketch out a goodly chunk of Plot into TR this weekend
and will do that modification.

My little POC of TRing the Hist* procedures ended translating pretty well.


The only "bump" I'm still seeing is in attempting to leverage Snip%  out of

When I try and type
(plot (Renderer-Tree ... stuff ... -> (U Snip% Void))

running  (test3) fails.

What I have now just stubs def-type Image-Snip% with Any, which isn't that
bad at all.

Is it because TR is currently invariant with Classes or did I tickle
another bug here?  Image-Snip% is a sub-type (class) of Snip%.

Say if typed/mred/mred explicitly proved a typed Image-Snip% would
everything work?


On Fri, Aug 10, 2012 at 3:00 PM, Neil Toronto <neil.toronto at gmail.com>wrote:

> On 08/10/2012 11:54 AM, Sam Tobin-Hochstadt wrote:
>> On Fri, Aug 10, 2012 at 1:38 PM, Ray Racine <ray.racine at gmail.com> wrote:
>>> Here https://gist.github.com/**3315984 <https://gist.github.com/3315984>
>>> The first (test1) works fine.  Note it uses a KW arg.
>>> However, (test2) fails.  I thought it was the complexity of the first arg
>>> that I was getting wrong.  But when the KW #:label is commented out it
>>> works
>>> fine.
>> What's happening here is that vectors don't subtype the way lists do,
>> so (Vector Symbol Flonum) isn't an appropriate value when you need a
>> (Vector Any (U Real False Interval)).  This isn't a problem when you
>> don't have the keyword argument, because Typed Racket can figure out
>> the needed types from the type of `discrete-histogram`, and so gives
>> the vector literals appropriate types.  However, TR doesn't currently
>> manage to propagate this information when looking at keyworded
>> applications, which are much more complex when expanded.  Thus the
>> behavior you're seeing.
>> If we give TR a little help here, then this works:
>> (define: lst : (Listof (Vector Any (U Real False Interval)))
>>    (list #(A 1.0) #(B 2.0) #(B 3.0) (vector 'C (ivl 0.5 1.5))))
>> (define (test2)
>>    (plot (discrete-histogram lst #:label "Hello")))
>> One way that `plot` could make this easier would be to support lists
>> in addition to vectors for histogram data.
> That wouldn't be hard to change. The contract and function are both
> defined in the file "plot/plot2d/rectangle.rkt". You want to take a crack
> at it, Ray? :)
> You should only have to change the contract of `cat-vals' in
> `discrete-histogram' (to se `or/c'), and change the match pattern that
> destructures it to (list (or (vector cats ys) (list cats ys)) ...).
> Neil ⊥
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