[racket-dev] Machinery for eliding contracts

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Mon Jun 9 18:00:01 EDT 2014

On Mon, Jun 9, 2014 at 8:35 AM, Sam Tobin-Hochstadt
<samth at cs.indiana.edu> wrote:
> On Mon, Jun 9, 2014 at 5:48 AM, Robby Findler
> <robby at eecs.northwestern.edu> wrote:
>> Am I right that the contract on 'f' is actually (-> symbol? any)? And
>> if so, where is the information coming from that lets you elide the
>> check?
> No, the `(boxof symbol?)` contract has to be kept around because of mutability.
>> One idea for this particular case: make 'g' be a macro that inspects
>> its argument and if it see "obvious" things like this, then it can
>> expand into a call to an unprotected use of 'g' instead of the
>> protected one. I'm not sure how general this would be, tho, but it has
>> two advantages: a) it can be done at compile time and b) it doesn't
>> need to deal with arbitrary contracts, only the ones generated by
>> types. Does that approach seem to have enough merit?
> I don't understand how this is supposed to work. If `g` was a macro,
> how would it know that `f` was something it could specialize on? Would
> every TR export also have some static information about its contract
> so that macros like `g` could recognize them?

Well, I was thinking it would have static information about its type,
actually. But yes.


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