[racket-dev] Machinery for eliding contracts

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Fri Jun 13 04:25:26 EDT 2014

Would it be useful to get blame information back from a value, just
like you can currently get the contract back?


On Tue, Jun 10, 2014 at 11:53 AM, Matthias Felleisen
<matthias at ccs.neu.edu> wrote:
> I was thinking of associating the contract with the type from which it comes and no that's not hash-consing. And if it's slower, too bad. -- Matthias
> On Jun 10, 2014, at 12:47 PM, Eric Dobson <eric.n.dobson at gmail.com> wrote:
>> On Tue, Jun 10, 2014 at 6:15 AM, Matthias Felleisen
>> <matthias at ccs.neu.edu> wrote:
>>> On Jun 9, 2014, at 6:02 PM, Eric Dobson <eric.n.dobson at gmail.com> wrote:
>>>>> Eric, are you talking about changing the proxy values that wrap HO/mutable
>>>>> contracted values?
>>>> Yes. I want the proxy values to include information about who agreed
>>>> to the contract in addition to the contract agreed to.
>>>> I actually realize that I might need more than just the contract
>>>> agreed to because of how TR changes the generated contract to remove
>>>> checks for what it guarantees, so that info is not in the contract.
>>>> But I believe that can be added back as a structure property on the
>>>> contract.
>>> Would some form of hash-consing contracts work here? -- Matthias
>> I don't think so. But not sure exactly what you are proposing.
>> The issue is that there are 4 contracts here and 2 of them currently
>> do not exist at runtime. The 4 are TRs checks/promises on an
>> export/import. (Using import for a value flowing into an exported
>> function). The promise contracts do not currently exist as removing
>> them was my previous optimization (They never fail). What I want to do
>> is change the check on import from (array/c symbol?) to (if/c
>> (protected>? (array/c symbol?)) any/c (array/c symbol?)). Where
>> (protected>? x/c) checks if TR already promised something stronger
>> than x/c.
>> I believe that you are proposing that we can use the identity of the
>> contract returned by value-contract to determine what the promised
>> contract would have been. This does not work as (Array Symbol) and
>> (Array Float) both get translated to (array/c any/c) for export, and
>> we would want to lookup different promised contracts for them. We
>> could use weak hash map as an extra field but that seems like it would
>> be slow.
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