for FAQ: what are use/require/import/refer?
This might make a good FAQ question: On Dec 20, 11:25 am, chris cnuern...@gmail.com wrote: I am unclear as to the difference between refer, import use, and require. Hi Chris, require: Load a Clojure library from a file on classpath. Use this when you want to load a library, but leave it in its own namespace. refer: Bring public symbols from one namespace into the current namespace. Use this when a library has already been loaded (example: clojure.set) but you want to use its public symbols without a namespace qualifier. import: Copy Java class names into current namespace. Use this when you want to use a Java class without typing the full package name. use: Combination of require and refer. Use this when you want to load a library AND use its symbols without a namespace qualifier. All four are available as keyword arguments to ns, which is the preferred way to use them: (ns foo.bar (:use my.little.lib) (:require clojure.contrib.duck-streams) (:import (java.io File InputStream)) (:refer clojure.set)) :require also allows aliasing, like this: (ns foo.bar (:require [clojure.set :as set])) Now you can write the symbol clojure.set/union as set/union. -Stuart Sierra --~--~-~--~~~---~--~~ 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 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 -~--~~~~--~~--~--~---
Re: for FAQ: what are use/require/import/refer?
This would make an excellent FAQ question and answer! On Sat, Dec 20, 2008 at 9:53 AM, Stuart Sierra the.stuart.sie...@gmail.comwrote: This might make a good FAQ question: On Dec 20, 11:25 am, chris cnuern...@gmail.com wrote: I am unclear as to the difference between refer, import use, and require. Hi Chris, require: Load a Clojure library from a file on classpath. Use this when you want to load a library, but leave it in its own namespace. refer: Bring public symbols from one namespace into the current namespace. Use this when a library has already been loaded (example: clojure.set) but you want to use its public symbols without a namespace qualifier. import: Copy Java class names into current namespace. Use this when you want to use a Java class without typing the full package name. use: Combination of require and refer. Use this when you want to load a library AND use its symbols without a namespace qualifier. All four are available as keyword arguments to ns, which is the preferred way to use them: (ns foo.bar (:use my.little.lib) (:require clojure.contrib.duck-streams) (:import (java.io File InputStream)) (:refer clojure.set)) :require also allows aliasing, like this: (ns foo.bar (:require [clojure.set :as set])) Now you can write the symbol clojure.set/union as set/union. -Stuart Sierra --~--~-~--~~~---~--~~ 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 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 -~--~~~~--~~--~--~---
Re: for FAQ: what are use/require/import/refer?
That really helped out a lot, thanks guys! As long as we are on the subject of helping out newbs... I like to program from the repl. I have a namespace that maintains some state, mainly integration with openGL. It has some essentially static variables that can't get initialized until openGL is initialized (like recording the version, vendor, extensions, and the renderer). I have put everything ui-related in one namespace called lambinator.ui. I have split this namespace up into two files, on for variable definitions and another for function definitions. The reason is that I usually don't want my variables cleared when reloading the file through load-file using the repl. I am using simple def's to define the variables; the ones that may be changed through opengl callbacks on other threads I am protecting with refs. So to be clear, I have: main-ns-file - this contains defs and calls load on the function file function def file - this gets loaded all the time when I am working in the repl. 1. Is using defs the best way to go about this? They are global variables; they model static state of the system, essentially. I might associate them with the main window, however, instead of global defs like they are now. 2. How do defs handle updating when I reload a file in the repl and then something in some other thread triggers a render? Lets say I change the render function which is called from the GLEventListener object on display. It is defined through a simple defn. Does this change propagate through to the other threads? Are defs themselves protected if they are at the module/file level? I was thinking maybe all the threads shared an environment which is itself a functional datastructure protected by refs... 3. If this is the case, do I need to protect my def'd variables with refs? 4. Is there some way to call load that ignores variable definitions if it has already seen them but does update function definitions regardless? 5. Finally, in the function-def file I have an in-ns definition, not a 'ns definition. This means that I *have* to use (import and (use, and I can't use :import or :use, correct? The documentation for in-ns didn't indicate that the keyword options were viable or I missed that piece of info. An answer to 4 would make 5 irrelevant. Again, thanks to everyone for their replies! Chris On Dec 20, 9:53 am, Stuart Sierra the.stuart.sie...@gmail.com wrote: This might make a good FAQ question: On Dec 20, 11:25 am, chris cnuern...@gmail.com wrote: I am unclear as to the difference between refer, import use, and require. Hi Chris, require: Load a Clojure library from a file on classpath. Use this when you want to load a library, but leave it in its own namespace. refer: Bring public symbols from one namespace into the current namespace. Use this when a library has already been loaded (example: clojure.set) but you want to use its public symbols without a namespace qualifier. import: Copy Java class names into current namespace. Use this when you want to use a Java class without typing the full package name. use: Combination of require and refer. Use this when you want to load a library AND use its symbols without a namespace qualifier. All four are available as keyword arguments to ns, which is the preferred way to use them: (ns foo.bar (:use my.little.lib) (:require clojure.contrib.duck-streams) (:import (java.io File InputStream)) (:refer clojure.set)) :require also allows aliasing, like this: (ns foo.bar (:require [clojure.set :as set])) Now you can write the symbol clojure.set/union as set/union. -Stuart Sierra --~--~-~--~~~---~--~~ 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 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 -~--~~~~--~~--~--~---
Re: for FAQ: what are use/require/import/refer?
On Dec 20, 12:44 pm, chris cnuern...@gmail.com wrote: 1. Is using defs the best way to go about this? They are global variables; they model static state of the system, essentially. Yes, global variables are probably best as Vars (which is what def creates). 2. How do defs handle updating when I reload a file in the repl and then something in some other thread triggers a render? Re-evaluating a def changes the root binding of a Var, which affects all threads but NOT in a protected, transactional way as with Refs. 3. If this is the case, do I need to protect my def'd variables with refs? If you want Ref-style transaction semantics, then yes. But if they are static values that don't change, then no. 4. Is there some way to call load that ignores variable definitions if it has already seen them but does update function definitions regardless? Yes, use defonce, which won't re-def things that already exist: clojure.core/defonce ([name expr]) Macro defs name to have the root value of the expr iff the named var has no root value, else expr is unevaluated 5. Finally, in the function-def file I have an in-ns definition, not a 'ns definition. This means that I *have* to use (import and (use, and I can't use :import or :use, correct? Not exactly. It's true, in-ns takes no other arguments. But typical usage would be something like this: top-level file my/cool/lib.clj: (ns my.cool.lib (:use ...) ; everything you need to use (:import ...) ; everything you need to import (:load my/cool/lib/part1 my/cool/lib/part2)) second file my/cool/lib/part1.clj: (in-ns 'my.cool.lib) third file my/cool/lib/part2.clj: (in-ns 'my.cool.lib) The top-level ns contains all the imports/uses/requires you need for the namespace, and the (:load ...) controls the order in which the subsidiary files are loaded. Each of the subsidiary files just does (in-ns ...), giving them access to everything used/imported in the top- level ns. I forgot whether the arguments to (:load ...) need slashes at the beginning. Either way, they're inside CLASSPATH. Ok, that was a lot; I hope some of it made sense. -Stuart Sierra --~--~-~--~~~---~--~~ 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 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 -~--~~~~--~~--~--~---
