A Challenge Problem for Promise Designers

Mark Miller erights at gmail.com
Sat Apr 27 10:20:37 PDT 2013

Sorry, I've been writing code with E style promises for, jeez, over 20
years now. (I suddenly feel very old :( .) I don't remember ever
experiencing the failure you're talking about. Can you give a concrete

On Sat, Apr 27, 2013 at 10:09 AM, Tab Atkins Jr. <jackalmage at gmail.com>wrote:

> On Sat, Apr 27, 2013 at 10:05 AM, Mark S. Miller <erights at google.com>
> wrote:
> > Are you distinguishing "autolifting" vs "lifting"? If so, why do you
> think
> > it is important or desirable to provide a lifting operation (as opposed
> to
> > an autolifting operation)?
> Because the "lifting" operation is the monadic lifting operation,
> which you need if you want to write monadic code that works
> predictably.  If all you have is an auto-lifter, your code will
> randomly fail sometimes in mysterious ways, because you're violating
> the monad laws.  (In a distinct, though thematically similar, way to
> how your code sometimes mysteriously fails if you use the Array
> constructor instead of Array.of().)
> ~TJ

Text by me above is hereby placed in the public domain

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