[racket] TR: Polymorphic types

From: Jordan Johnson (jmj at fellowhuman.com)
Date: Sun Jan 18 19:14:45 EST 2015

Hi Sam & Matthias,

Thanks for the clarification.

And thanks to Alexander for pointing out the typed/json module — been a while since I’ve pulled down a nightly build.

Speaking of that: with the splitting of the repos, if I want to contribute code to the TR repository, is there a quick reference doc yet for running that repo’s code against an existing Racket installation (or a clone of the main racket repo)? (The first time I wrote a TR wrapper lib, I found Greg Hendershott’s “Guide for Infrequent Contributors <http://www.greghendershott.com/2013/04/a-guide-for-infrequent-contributors-to-racket.html>” tremendously helpful in getting over the initial hump in the Racket+Git learning curve — so I suppose I’m hoping the procedure will be similarly straightforward, post-split.)

Thanks again,
jmj

> On Jan 18, 2015, at 12:16 PM, Sam Tobin-Hochstadt <samth at cs.indiana.edu> wrote:
> 
> I've added an example of this to the documentation.
> 
> Sam
> On Sat Jan 17 2015 at 9:48:36 PM Matthias Felleisen <matthias at ccs.neu.edu <mailto:matthias at ccs.neu.edu>> wrote:
> 
> On Jan 17, 2015, at 9:32 PM, Sam Tobin-Hochstadt wrote:
> 
> > No, it can't be adapted. That error message is an instance of this
> > caveat: http://docs.racket-lang.org/ts-guide/caveats.html#%28part._.Typed-untyped_interaction_and_contract_generation%29 <http://docs.racket-lang.org/ts-guide/caveats.html#(part._.Typed-untyped_interaction_and_contract_generation)>
> > which applies to `define-predicate` as well. There's no way to check
> > if something is a `Foo`, because Typed Racket wouldn't know what you
> > meant for `A` to be.
> 
> 
> I think the section [title] is misleading here. You need to know
> TR's ideas well to see that the generation of a run-time object
> is the same thing as moving from the typed to the untyped world
> (and vice versa).
> 
> Perhaps an example like Jordan's could be included in the docs.
> 
> -- Matthias
> 
> 
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