Hi Ben, On Fri, Mar 7, 2014 at 11:02 AM, ben <[email protected]> wrote:
> Thanks, John. > > I am still a little confused: > > (1) Does the main module of a package have to be named like the package? > No, but when you type "using Pkg" or "import Pkg", Julia looks first in the the current directory for Pkg.jl, and if not there, it searches the package directory ($HOME/.julia/v0.3), and the LOAD_PATH for the following: 1. Pkg.jl 2. Pkg/src/Pkg.jl 3. Pkg.jl/src/Pkg.jl (The relevant lines are at the beginning of https://github.com/JuliaLang/julia/blob/master/base/loading.jl.) So if you rename the package and then try to use "using MyPkg" or "import MyPkg", Julia will be looking for the wrong package name. You can get around this with require("GalaxyBlue/src/Galaxy.jl") # or require("GalaxyBlue/src/Galaxy") -- the .jl is optional using Galaxy # Finds the Galaxy module you just required I've opened up an issue to clarify this ( https://github.com/JuliaLang/julia/issues/6082). > (2) What is the priority of modules/packages when, eg, calling `import > Galaxy` if there is both a package and a module named Galaxy (see example > below)? > This should hopefully be clarified by the answer to (1) above. > (3) What is the correct use of import/using/require? > Some of this is described here: http://julia.readthedocs.org/en/latest/manual/modules/ although it should probably be updated. Briefly: 1. "using MyModule" imports all of the exported functions of MyModule into the current namespace 2. "import MyModule" imports the module name; functions can be called with " MyModule.fn(x,y)" 3. "import MyModule: fn1, fn2" imports the functions "fn1" and "fn2" into the current namespace 4. "require("somefile.jl")" loads a particular file. This is useful when: a. you have a script or some bare function definitions you wish to load/execute from another file or at the REPL b. a file defines a module with a different name than the filename (as in my answer to #1 above) > (4) What is the point of the (documented) syntax > `Pkg.clone("github/fork/url/Galaxy.jl.git", "GalaxyBlue")`? Is it > deprecated? Is it exactly equivalent to a git clone from terminal? > Pkg.clone("http://github.com/myid/SomePackage.jl";) is meant to clone a package that might not be in the official list. It is equivalent to git clone in the Julia package directory, with the only difference that it strips ".jl" from the name (but Julia will find the package contents either way--see the answer to 1 above). I'm not familiar with the second parameter, but I assume it does what you ask. > > Here is an example which can happen in practice and which is very unclear > to me: > > [Package Galaxy] > module Galaxy > (stuff) > module Star > using Galaxy > (stuff) > end > end > > [Forked Package GalaxyBlue] > module Galaxy > (stuff) > module Star > using Galaxy <-------------------------------- what > happens here? is it going to use the forked version or load the package > Galaxy? > (stuff) > end > end > Testing: kevin@IsiahThomas:~/.julia/v0.3$ find Galaxy Galaxy Galaxy/src Galaxy/src/Galaxy.jl kevin@IsiahThomas:~/.julia/v0.3$ cat Galaxy/src/Galaxy.jl module Galaxy println("Galaxy") end kevin@IsiahThomas:~/.julia/v0.3$ julia -e 'using Galaxy' Galaxy kevin@IsiahThomas:~/.julia/v0.3$ find GalaxyQuest GalaxyQuest GalaxyQuest/src GalaxyQuest/src/Galaxy.jl kevin@IsiahThomas:~/.julia/v0.3$ cat GalaxyQuest/src/Galaxy.jl module Galaxy export galaxy galaxy() = "Milky Way" module Star using Galaxy println(Galaxy.galaxy()) end end kevin@IsiahThomas:~/.julia/v0.3$ julia -e 'require("GalaxyQuest/src/Galaxy"); using Galaxy.Star' Milky Way This is what would be expected, actually, since the Galaxy definition is already loaded. No magic. If the module definition exists, it's used. Hope this is helpful! (If you wanted to take this answer and update the documentation, a pull request would be very much appreciated.) Cheers, Kevin > (I found a somewhat related discussion here: > https://groups.google.com/forum/#!topic/julia-users/5TAUsNfZmqE > ) > > Ben > > > > > On Tuesday, February 25, 2014 11:28:40 AM UTC-5, John Myles White wrote: > >> I think the core insight is that a package has two components: >> >> (1) A module called GalaxyBlue >> (2) A file, in a searchable package directory like Pkg.dir(), that’s >> called something like GalaxyBlue/src/GalaxyBlue.jl. >> >> For 2, that means you have a directory (usually a repo) containing the >> package code, a subdirectory called src and then a file called >> PACKAGENAME.jl, which will be automatically loaded. That file should >> contain the definition of your module. >> >> I’m not sure, but I suspect that Pkg.clone with a second argument isn’t >> changing the content of that file. >> >> — John >> >> On Feb 25, 2014, at 7:01 AM, ben <[email protected]> wrote: >> >> > Hi, >> > >> > Is it possible for two different packages to contain identically named >> modules? >> > >> > For instance, if I fork a package Galaxy.jl, and then >> > >> > > Pkg.clone("github/fork/url/Galaxy.jl.git", GalaxyBlue) >> > >> > (So that both the original package and my forked version live >> side-by-side in my .julia repository.) How do I then use GalaxyBlue? "using >> GalaxyBlue" and "require("GalaxyBlue")" both give me "ERROR: GalaxyBlue" >> not found. >> > >> > I guess I am generally confused about package names v. module names and >> I was not able to find documentation on this. >> > >> > Thanks! >> > >> > Ben >> >>
