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Re: The Paradox of Partial Parametricity

From: Andreas Rossberg <rossberg@google.com>
Date: Fri, 10 May 2013 21:05:34 +0200
Message-ID: <CADjR9No5MA1pk_OhWftiqJB=HtygNn=UwU+SxgBZu=_ioiwa4g@mail.gmail.com>
To: "Mark S. Miller" <erights@google.com>
Cc: Jonas Sicking <jonas@sicking.cc>, "Tab Atkins, Jr." <jackalmage@gmail.com>, Domenic Denicola <domenic@domenicdenicola.com>, "public-script-coord@w3.org" <public-script-coord@w3.org>
On 10 May 2013 14:52, Mark S. Miller <erights@google.com> wrote:
> An upper case type variable, e.g. T, is fully parametric. It may be a
> promise or non-promise.
> A lower case type variable, e.g. t, is constrained to be a non-promise. If
> you wish to think in conventional type terms, consider Any the top type
> immediately split into Promise and non-promise. Thus type parameter t is
> implicitly constrained to be a subtype of non-promise.

Mark, I'm afraid such a distinction makes absolutely no sense in a
world of structural types. How would you specify the set of "types
that aren't promises" in a way that is compatible with structural
subtyping?

/Andreas
Received on Friday, 10 May 2013 19:13:50 UTC

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