I see - thanks very much Stephen, that's very helpful. So it seems like this check should only catch circular dependencies when they appear in ns forms, since those will produce a cycle error if none of the other namespaces are currently loaded. I'll investigate doing this. I can't think of a case when you wouldn't want this check, since when a cycle exists in ns forms there should be no way to load any of the related namespaces without receiving an error.
Cheers, Colin On 17 October 2014 18:04, Stephen Gilardi <scgila...@gmail.com> wrote: > > So, I'm confused. I'm not sure what is allowed and under what > circumstances, and I'm not sure what I should be validating here. Zach very > reasonably argued that Clojure clearly permits this since Manifold works, > but I'm not sure if this is just a happy accident. Looking at the > clojure.core code, it seems that there is only circular dependency checking > when using load, not when using require. > > I took a look at what’s going on in the manifold case. I’m not sure this > explanation is enough to yield a solution to the problem you’re trying to > solve, but it should be a good start. > > The cyclic load dependency check fails if `load` is asked to load a file > while that same file has started loading but not yet finished loading. It’s > a runtime check. > > `require` calls `load` conditionally to implement its basic function: > “load a lib if it isn’t already loaded”. `require`’s processing of a given > libspec may or may not result in a call to `load`: If the lib is already > loaded, it isn’t loaded again. > > As of commit f11e70726553685bda222ccd37c28addcfc519c7 (29 November 2012, > first in clojure-1.5.0-beta2), a lib is considered loaded as soon as an ns > form for the corresponding namespace has been successfully evaluated. > > In the case of manifold.stream, the explicit calls to `require` occur > after (ns manifold.stream …). Since manifold.stream is already considered > loaded at that point, the indirect calls to (require ‘manifold.stream) that > they generate do not result in calls to `load` and therefore do not trigger > the cyclic load dependency check. > > —Steve > > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
