[racket-dev] Racket2 suggestion: Attaching properties to operators

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Sun May 5 12:58:52 EDT 2013

On May 5, 2013, at 12:51 PM, Laurent wrote:

> On Sun, May 5, 2013 at 6:44 PM, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
> C++ has tried this tack for some time.
> Sounds like it has failed then.
> I can see doing for built-ins but how would you go about programmer-created operations? Trust the programmer? -- Matthias
> Well, I guess some checks can be added, but I don't see the difference between attaching bad properties to a newly created operator and defining a buggy procedure.

I think it is one thing to say 

  (define (fahrenheit->celsius f) 32)

and another to attach "associative" to the floating-point + operator. Since we all write examples first and translate then into test suites before we code, finding a bug in fahrenheit->celsius is straightforward and supported by our support mechanisms. If you don't trust your tests, attach contracts to your procedures because they generalize tests in a natural way. Finding bugs in false claims about functions is much less supported at the moment. Perhaps random testing or model checking or something like that may help along here. 

-- Matthias

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