[racket-dev] [plt] Push #24906: master branch updated

From: Asumu Takikawa (asumu at ccs.neu.edu)
Date: Mon Jun 25 23:04:17 EDT 2012

On 2012-06-25 20:17:33 -0600, Ryan Culpepper wrote:
> IIUC from your later message, you've implemented the generics
> analogue of object/c (per-instance contract), whereas
> prop:dict/contract is closer to class/c (per-type contract). It's a
> little fuzzy because prop:dict/contract hacks in per-instance
> contracts too in a kind of ad hoc way.

That's a good point. The better analogy might be interface contracts vs.
class/c. With generics, it is easy to control all points that an
instance is created since constructors are just procedures. With
classes, you can't get away with that since the instantiation forms are

The difference/advantage you might get with a per-type contract for
generics is that you get a more interface-like blame story, as with
interface contracts. Coverage isn't as much of an issue since you can
just contract all constructors.

Unfortunately, it's also not clear how to implement interface-like
contracts for generics. Since the generics forms don't control the
constructors, it's not obvious how to instantiate the blame at the
construction site.


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