clojure

问题 I am trying to show the importance of lazy-sequences or lazy-evaluation to the non-FP programmers. I have written this implementation of prime-generation to show the concept: (defn primes-gen [sieve] (if-not (empty? sieve) (let [prime (first sieve)] (cons prime (lazy-seq (primes-gen (filter (fn [x] (not= 0 (mod x prime))) (rest sieve)))))))) ;;;;; --------- TO SHOW ABOUT THE LAZY-THINGS ;; (take 400 (primes-gen (iterate inc 2))) ;; (take 400 (primes-gen (range 2 1000000000000N))) However, i

问题 I'm passing my macro to a map operation (which is also a macro). I'm having some trouble getting my values out. Here is an example: (def num-vec [1 2 3 4 5]) (defmacro describe-args [first-arg & remaining-args] `(println '~first-arg '~remaining-args)) (doall (map #(describe-args "my args " %) num-vec)) This returns: my args (p1__432#) my args (p1__432#) my args (p1__432#) my args (p1__432#) my args (p1__432#) My question is: How do I get the argument in a macro from a map macro in Clojure? (I

问题 In Ruby, there is Kernel#Array method, which acts like this: Array([1, 2, 3]) #=> [1, 2, 3] Array(1..5) #=> [1, 2, 3, 4, 5] Array(9000) #=> [9000] Array(nil) #=> [] In other words, it converts nil to empty array, non-collections to singleton arrays, and kinds of collection-like objects (i.e. objects which respond to #to_ary or #to_a ) to arrays. I want to have something similar to this in Clojure: (to-seq [1 2 3]) ;=> (1 2 3) (to-seq (range 1 5)) ;=> (1 2 3 4) (to-seq 9000) ;=> (9000) (to-seq

问题 I'm now making a class object with Clojure which has a method returning the object itself. Written with Java, the object that I'd like to make is like, class Point { public double x; public double y; public Point(double x, double y) { this.x = x; this.y = y; } public Point copy() { return new Point(this.x, this.y); } } The current clojure code that I wrote is like, (ns myclass.Point :gen-class :prefix "point-" :init init :state state :constructors {[double double] []} :methods [[copy []

问题 When I have a space-separated key, how can I use it to extract a value without re-creating the key? I have a set of potential keys, column names actually, as the first sequence in data returned from clojure-csv: (This is formatted to avoid scrolling.) ["AGY/DIV " "STS" "GIC-ID " "LAST-NAME " "FIRST-NAME " "COVERAGE DESCRIPTION " "PREMIUM " "RUN-DATE" "BIL MO "] Then I create keys from this row and zipmap the keys with each subsequent row (sequence) of data: (defn create-map-keys "Takes a

问题 In common lisp I can do this: src-> (defmacro macro-hello () `"hello") (eval '(macro-hello)) no problem. In clojure: (defmacro macro-hello [] `"hello") (eval '(macro-hello)) gives me an error. Have I done something wrong? Clojure Error: Exception in thread "main" java.lang.Exception: Unable to resolve symbol: macro-hello in this context (NO_SOURCE_FILE:12) at clojure.lang.Compiler.analyze(Compiler.java:4340) at clojure.lang.Compiler.analyze(Compiler.java:4286) at clojure.lang.Compiler

问题 I have a vector of maps, that I'd like to transform in a nested fashion. The data is structured as follows: (def data [{:id 1 :name "a" :parent 0} {:id 2 :name "b" :parent 0} {:id 3 :name "c" :parent 0} {:id 4 :name "a_1" :parent 1} {:id 5 :name "a_2" :parent 1} {:id 6 :name "b_1" :parent 2} {:id 7 :name "a_1_1" :parent 4}]) Each map has an :id , some other keys and values not important for this discussion, and :parent key, denoting if the elements belong to another element. If :parent is 0,

问题 I've been struggling a bit trying to get this to work. Getting clojure 1.3 was a breeze, but now I've been trying to get contrib libraries to install and I get errors. Is there a guide on how to do this correctly? 回答1: The old clojure.contrib monolithic library is incompatible with clojure 1.3. See http://dev.clojure.org/display/design/Where+Did+Clojure.Contrib+Go As for how to install libraries correctly, either write your own pom.xml and use maven or use leiningen (much easier!) - https:/

问题 This is one of those "Is there a built-in/better/idiomatic/clever way to do this?" questions. I want a function--call it fn-pow --that will apply a function f to the result of applying f to an argument, then apply it to the result of applying it to its result, etc., n times. For example, (fn-pow inc 0 3) would be equivalent to (inc (inc (inc 0))) It's easy to do this with iterate : (defn fn-pow-0 [f x n] (nth (iterate f x) n)) but that creates and throws away an unnecessary lazy sequence. It

问题 Runnig lein for the first time, it installs clojure, but were to? It does not seem to be in /Library ... ~/Library ... ~/.lein ... Is there an established location for clojure.jar and the contribution jars on Unix/OS X## Heading ##? 回答1: Leiningen uses maven (or, to be more precise, the underlying libs which implement maven), which by default will install all dependencies under $HOME/.m2/ . 回答2: The default path is given by (.getPath (clojure.java.io/file (System/getProperty "user.home") ".m2