clojure

问题 I came across google guice and could not really understand it and what it did, although there seems to be alot of hype around it. I was hoping to get a clojurian perspective of the library and why it is needed/not needed in clojure applications and if there was anything similar built into the language. 回答1: Because of Java's OO and type system, dynamically switching between different underlying implementations (for test (mocking) purposes for instance) can be difficult to manage. Libraries

问题 In Clojure, I would like to combine several maps into a single map where mappings with same key are combined into a list. For example: {:humor :happy} {:humor :sad} {:humor :happy} {:weather :sunny} should lead to: {:weather :sunny, :humor (:happy :sad :happy)} I thought about: (merge-with (comp flatten list) data) But it is not efficient because flatten has O(n) complexity. Then I came up with: (defn agg[x y] (if (coll? x) (cons y x) (list y x))) (merge-with agg data) But it feels not

问题 On REPL, if I define (def fits (map vector (take 10 (iterate inc 0)))) and then call (== [2] (nth fits 2)) I get false. But (= [2] (nth fits 2)) returns true. Is this expected ? I tried (class [2]) and (class (nth fits 2) and both return Persistent Vector. 回答1: == is for comparing numbers. If either of its arguments is not a number, it will always return false: (== :a :a) ; => false As you can see by saying (clojure.contrib.repl-utils/source ==) at the REPL (with repl-utils require 'd, of

问题 I've seen the ^:static metadata on quite a few function in the Clojure core.clj source code, e.g. in the definition of seq? : (def ^{:arglists '([x]) :doc "Return true if x implements ISeq" :added "1.0" :static true} seq? (fn ^:static seq? [x] (instance? clojure.lang.ISeq x))) What precisely does this metadata do, and why it it used so frequently throughout core.clj ? 回答1: In the development of Clojure 1.3 Rich wanted to add the ability for functions to return types other than Object. This

问题 How can I run a clojure script from matlab? I tried following: run matlab with jdk 1.7 and then call java MATLAB_JAVA=/usr/lib/jvm/java-7-oracle/jre matlab in the matlab, set classpath and use clojure compiler javaaddpath([pwd '/lib/clojure-1.5.1.jar']) import clojure.lang.RT Here I got error: Error using import Import argument 'clojure.lang.RT' cannot be found or cannot be imported. When I writing java class that runs clojure, everything working from console, but whould not run from matlab.

问题 How can I wrap a string in an input-stream in such a way that I can test the function bellow? (defn parse-body [body] (cheshire/parse-stream (clojure.java.io/reader body) true)) (deftest test-parse-body (testing "read body" (let [body "{\"age\": 28}"] ;; must wrap string (is (= (parse-body body) {:age 28})) ))) 回答1: It is straightforward to construct an InputStream from a String using host interop, by converting to a byte-array first: (defn string->stream ([s] (string->stream s "UTF-8")) ([s

问题 In the compojure library in the core namespace, I see the following form: (defn- compile-route "Compile a route in the form (method path & body) into a function." [method route bindings body] `(#'if-method ~method (#'if-route ~(prepare-route route) (fn [request#] (let-request [~bindings request#] (render (do ~@body) request#)))))) and (defmacro GET "Generate a GET route." [path args & body] (compile-route :get path args body)) Further up in the file, the if-method and if-route functions are

问题 I need to consume a WSDL web service and the Java client-side code I've seen so far looks bloated and complicated. I was wondering whether a cleaner solution might exist in Clojure so that I may perhaps implement that part in Clojure and expose a simpler API to the Java code. 回答1: cd your_project_dir/src wsimport -p some.import.ns http://.../service?wsdl It would create ./some.import.ns/*.class . So you can just use them in your clojure project (ns your.ns ... (:import [some.import.ns some_WS

问题 With the following code, I can add a permission using my AWS account number but the queue does not receive any messages from SNS. AddPermissionRequest addPermissionRequest = new AddPermissionRequest(); addPermissionRequest.ActionName.Add("SendMessage"); addPermissionRequest.ActionName.Add("ReceiveMessage"); addPermissionRequest.QueueUrl = queueUrl; addPermissionRequest.Label = General.IpAddressAWSFriendly; addPermissionRequest.AWSAccountId.Add(AWS_ACCOUNT_ID); sqs.AddPermission

问题 I would like to define my own reader macro in clojure: (read-string "ßfoo") => (some_func :foo) Is it possible? 回答1: It is possible to create tagged literals by having a reader map in data_readers.clj at the top of your classpath. This must be in data_readers.clj at the top of your classpath (usually src directory). {ß reader-demo.core/read-fn} This goes into reader-demo.core (defn some-func [arg] (str "some-func invoked with " arg)) (defn read-fn [arg] (-> arg keyword some-func)) Invoking #ß