On Sunday, December 28, 2014 9:24:38 PM UTC-5, Mike Innes wrote: > > I can only speculate about the reason that people still use include, even >> though Julia has nice modules. > > > Well, I for one think that > > 1) Modules containing a large number of functions are OK (and this is very > common in more functional languages) > 2) If you're going to have (1), you want to split that module across > multiple files. > > Languages which embrace (1) but conflate modules and files tend to end up > looking like this > <https://github.com/clojure/clojure/blob/master/src/clj/clojure/core.clj>. > Personally, I prefer the Base's organisation, and would be happy to never > see a 7,000 line Julia file. >
I'm in complete agreement with both of your points here--I'm just saying that `include` is a problematic way of achieving these goals. To rephrase it again, the main thing that I don't like about `include` is that when you are reading a file that ends up being included somewhere else, in general you have to know what context it is going to be included in to know how it will work. That information is not present in the file itself. This essentially forces you to understand new packages in a top down way (because you must first find all of the `include` statements), instead of having the option of reading them bottom up or top down. The main useful property of a module over a naked `include` is that when you are reading the module, all of the relevant information about scope is present in the file itself, instead of existing in a different file at the `include` site. I haven't done a careful analysis, but I hypothesize that if you look at how `include` is used in high quality packages, you will generally find that included files don't actually use the scope of the environment they are included into, so from that standpoint, they could usually be modules instead. But I bet you'll also find a few instances where they do use that scope, and you'll never know when without a close reading. This is why I'm suggesting that maybe what Julia needs is better mechanisms for composing small modules into larger modules. The goal would be to achieve your points (1) and (2) without having lots of files that run in a mystery scope.
