Comments on: Broken Promises

By: jayprich

jayprich — Mon, 26 Aug 2013 16:58:29 +0000

Excel’s lazy evaluation tree is pretty efficient and parallel. The functions are supposed to be stateless without side-effects, you can break that with VBA of course.

The scattering of the execution path is a core issue for this programming style that can only be solved with better tools, e.g. ability to display the ‘trace’ for debug.

It seems your complaint is not about a “promise” per-se but that Objective-C and it’s libraries do not guarantee a functional style outside Grand Central Dispatch and Blocks (closures).
Do you think iOS 7’s multitasking will help address the issues that you say “promises” don’t?

It does seem a number of people haven’t given up trying this direction of development:
https://github.com/mogeneration/functionalkit
https://github.com/stuartervine/OCTotallyLazy
https://github.com/leuchtetgruen/functional.m
( OCaml used in an iOS app http://psellos.com/ocaml/example-app-slide24.html )

By: Joe

Joe — Mon, 12 Aug 2013 15:55:00 +0000

@Tane That just isn’t true. I’ve been quite annoyed by the fact that Python doesn’t have do-while loops numerous times. As a matter of fact, I have a Visual Studio window open next to the browser and there is currently a do-while loop on screen. They have their uses.

By: Marek Sieradzki

Marek Sieradzki — Mon, 05 Aug 2013 19:52:54 +0000

What you’re talking about sounds a lot like space leaks in Haskell caused by laziness. It seems that you’re explaining it using different words but mean exactly the same thing.

By: Lior Bar-On

Lior Bar-On — Sun, 21 Jul 2013 07:09:27 +0000

Thanks for a Great Article!

It does indeed seem Promises are a bit overrated, and it good you nailed down some of its downsides.

I don’t feel I’m the right person to do that, but I think some of the issues you raised (e.g. memory consumption) would also happen in naive callback-based implementation.

All in all this doesn’t change the overall conclusion, that Promises are not silver bullets.

Lior

By: Tane

Tane — Fri, 19 Jul 2013 05:53:19 +0000

“The war between promises and callbacks is kind of like the war between while loops and for loops.”

I love the unspoken understanding that no-one uses do-while loops. 😛

By: Andy Matuschak

Andy Matuschak — Wed, 10 Jul 2013 20:38:44 +0000

This is an excellent case study for API authors, Drew; thank you. I really appreciate all the detailed explanations of the failure modes and the paths you took to get there, rather than the hand-waving hate one typically reads.

By: Jason Mulligan

Jason Mulligan — Fri, 10 May 2013 16:20:33 +0000

Haters gonna hate.

You clearly haven’t figured out the appropriate place to utilize the pattern, but you nailed the “I don’t like this! rawr!” part common to devs these days.

Congrats.