I would say that this module is handling "control flow" not "flow control".
-- Daniel R. <[email protected]> [http://danielr.neophi.com/] On Tue, Dec 11, 2012 at 10:59 AM, Forrest L Norvell <[email protected]>wrote: > From a brief look, this looks very similar to the model used by TameJS or > Iced CoffeeScript, both of which use an approach rooted in await / deferred > semantics and AST parsing and rewriting. Are you aware of those projects? > If so, how is your approach different? Also, aside from slightly terser > syntax, what does this approach offer over promises, which don't require a > preprocessing step? > > I don't intend to sound dismissive or hostile, but there are a massive > number of flow control libraries for JS / Node, and a considerable > amount of this list's history tied up in arguing their relative merits, > which is part of the reason why Node has such a minimal / primitive model > for dealing with continuations in the first place. New flow control tools > are unlikely to see much uptake unless they bring something significant and > new (that justifies the time taken to learn them and the cost of > maintaining code that looks different from more idiomatic JS) to the table. > > F > > > On Monday, December 10, 2012, Jonathan Dickinson wrote: > >> Hi All, >> >> I just started my first foray into javascript beyond the usual minimal >> glue I was used with browsers. After looking at some node tutorials the >> first thing I noticed was the CPS hell (honestly, no way in hell I am >> dealing with that ;)). I present an extremely rough draft of asyncscript; >> it modelled after (black-box) looking at how C# implements its async. >> https://github.com/jcdickinson/asyncscript >> >> The metacompiler first takes an AST (lightly modified acorn.js) and turns >> in into IR. The IR basically adds blocks and closures to the AST, so you >> essentially land up with: >> >> - Closure >> - Block1 >> - AST >> - Block2 >> - AST >> - Block3 >> - AST >> - Closure >> - ... >> - AST >> >> Blocks are breaks in real execution (read: continuations - although I >> will also need to [ab]use them for branching constructs in the presence of >> the async keyword). The IR is then passed off to a few transformation >> stages (async, if, &&/||, while, for - of which only async is implemented). >> So for example, the async transform will create a split in the block >> (resulting in two blocks) at the statement containing the async keyword. >> >> - Closure (async) >> - Block1 >> - AST that was in Block1 before await >> - await >> - Block2 >> - grab async result >> - AST that was in Block1 after await >> >> Finally the IR is turned into JS. Due to the lack of a goto statement in >> JS I needed to implement 'transitioning' blocks (if, and other >> non-continuation branches) as a while loop: >> >> var state = 0; >> while(true) { >> switch(state) { >> case 0: >> blar(); >> state = 1; // Effectively a goto >> break; >> case 1: >> baz(); >> return; >> } >> } >> >> Yes, it's ugly, but I would rather have ugly code than bloating the call >> stack (please, does anyone has any better ideas how to do this without >> wasting stack space?). 'sequencing' blocks simply return out of the >> function after registering the continuation. So at the end of the day you >> get: >> >> asyncscript: >> var username = "jimbob"; >> var settings = await httpGetAsync("http://myserver/?username="; + >> username); >> await displaySomeModal(settings); >> >> javascript (tidied): >> (function () { >> var state = 0; >> var awaiter = createAwaiter(); >> function continuation() { >> try { >> var result = arguments[1]; >> if (typeof arguments[2] !== 'undefined') throw arguments[2]; >> state = arguments[0]; >> while (true) { >> switch (state) { >> case 0: { >> username = "jimbob"; >> await(continuation, 1, httpGetAsync(" >> http://myserver/?username="; + username)); >> return; >> } >> case 1: { >> tmp = result; >> settings = tmp; >> await(continuation, 2, >> displaySomeModal(settings)); >> return; >> } >> case 2: { >> completeAwaiter(continuation); >> return; >> } >> default: >> throw 'The runtime has become unstable.'; >> } >> } >> } catch (error) { >> completeAwaiter(continuation, null, error); >> return; >> } >> } >> continuation(0); >> return createPromise(awaiter); >> })(); >> >> As I said, this is my first serious attempt at JS - so I might have made >> some obvious mistakes (quite possibly messing up the closure semantics, but >> I think I got it right). Feel free to tell me (in a justified way) how I am >> a noob :), also remember that this is a draft: so a very small amount of >> the JS syntax is actually implemented. I would just like some feedback >> before making something that is complete but blatantly incorrect. >> >> I am also [ab]using AMD for the purposes of loading in different >> 'runtimes' (code generators that define how e.g. completeAwaiter and >> createPromise, are generated) for the purposes of e.g. jquery v.s. >> node-promise. I might be doing the totally wrong thing, but thought it was >> pretty cool. I will also fix the folder layout some time later: at the >> moment it hacks in intellisense support for VS2012. >> >> If you think it's beyond help and want to re-implement it, I don't mind >> at all: I would be happy to contribute code and ideas to a repo maintained >> by someone who knows what they are doing. >> >> -- >> jcd >> >> -- >> Job Board: http://jobs.nodejs.org/ >> Posting guidelines: >> https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines >> You received this message because you are subscribed to the Google >> Groups "nodejs" group. >> To post to this group, send email to [email protected] >> To unsubscribe from this group, send email to >> [email protected] >> For more options, visit this group at >> http://groups.google.com/group/nodejs?hl=en?hl=en >> > -- > Job Board: http://jobs.nodejs.org/ > Posting guidelines: > https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines > You received this message because you are subscribed to the Google > Groups "nodejs" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/nodejs?hl=en?hl=en > -- Job Board: http://jobs.nodejs.org/ Posting guidelines: https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines You received this message because you are subscribed to the Google Groups "nodejs" group. 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