Function composition Clojure?
Can Clojure implement (g ∘ f) constructions like Haskell's g . f? I'm currently using workarounds like (fn [n] (not (zero? n))), which isn't nearly as nice :) ...
clojure
Vectors or Java arrays for Tetris?
I'm trying to create a Tetris-like game with Clojure and I'm having some trouble deciding the data structure for the playing field. I want to define the playing field as a mutable grid. The individual blocks are also grids, but don't need to be mutable. My first attempt was to define a grid as a vector of vectors. For example an S-block...
Dynamically generating high performance functions in clojure
I'm trying to use Clojure to dynamically generate functions that can be applied to large volumes of data - i.e. a requirement is that the functions be compiled to bytecode in order to execute fast, but their specification is not known until run time. e.g. suppose I specify functions with a simple DSL like: (def my-spec [:add [:multiply...
Returning from a function while inside one or more nested loops?
Is there a way to immediately return from a function when in one or more nested loops? Here's some sample code illustrating the problem: ; Grid data structure ; ------------------- (defstruct grid :width :height) (defn create-grid [w h initial-value] (struct-map grid :width w :height h :data (ref (vec (repeat (* w h) ...
How to run Clojure tests on Windows?
I put Clojure in C:\clojure-1.1.0, and start the REPL by: java -cp clojure.jar clojure.main In \test\clojure\test_clojure, there are a bunch of test files. How to run these? For example, I tried: java -cp ......\clojure.jar clojure.main data_structures.clj And it didn't work. ...
Clojure: using *command-line-args* in the script rather than REPL
I've clojure running within Eclipse. I want to pass arguments to clojure when running it. In the below the arguments are available in the REPL but not in the script itself. What do I need to do such that in the below typing arg1 in the REPL will return the first argument? Script: (NS Test) (def arg1 (nth *command-line-args* 0)) After...
How to rename an operation in Clojure?
In my list, addition, the operation + appears as #. How can I make this appear exactly as +? When I eval it, it should also work exactly the same as +. I guess this would also apply in all kinds of functions in Clojure... Thanks guys. ...
Alternatives to java on android
Hello guys, I just got myself an android phone and I'm dying to start coding on it ! However I'm not a big java fan, although I can live with that, I would like to know if there're reasonable alternatives for the android virtual machine. I've done a medium sized project using clojure, however from the reviews I read, it's very slow when ...
Atoms and references
According to the book Programming Clojure refs manage coordinated, synchronous changes to shared state and atoms manage uncoordinated, synchronous changes to shared state. If I understood correctly "coordinated" implies multiple changes are encapsulated as one atomic operation. If that is the case then it seems to me that coordination o...
Controlling symbol generation in Clojure macros
I'm trying (as a self-learning exercise) to create a Clojure macro that will generate code to apply a function to a sequence of integers and sum the result, e.g. f(0) + f(1) + f(2) + f(3) This is my attempt: (defmacro testsum [func n] `(fn [x#] (+ ~@( map (fn [i] `(~func x#)) (range n))))) However something seems to go wrong wit...
How do nested dosync calls behave?
What happens when you create nested dosync calls? Will sub-transactions be completed in the parent scope? Are these sub-transations reversible if the parent transaction fails? ...
How to break out from nested doseqs
Hi, I have a question regarding nested doseq loops. In the start function, once I find an answer I set the atom to true, so that the outer loop validation with :while fails. However it seems that it doesn't break it, and the loops keep on going. What's wrong with it? I am also quite confused with the usage of atoms, refs, agents (Why do...
why can't I call .update on a MessageDigest instance
when i run this from the repl: (def md (MessageDigest/getInstance "SHA-1")) (. md update (into-array [(byte 1) (byte 2) (byte 3)])) I get: No matching method found: update for class java.security.MessageDigest$Delegate the Java 6 docs for MessageDigest show: update(byte[] input) Updates the digest using the specifie...
How to map a test onto a list of numbers
I have a function with a bug: user> (-> 42 int-to-bytes bytes-to-int) 42 user> (-> 128 int-to-bytes bytes-to-int) -128 user> looks like I need to handle overflow when converting back... Better write a test to make sure this never happens again. This project is using clojure.contrib.test-is so i write: (deftest int-to-bytes-to-int ...
Wrong number of args passed to: repl$repl
Hi, I have a trouble with a compojure "Getting started" example that I do notunderstand. When I run the example from http://weavejester.github.com/compojure/docs/getting-started.html ...I get the following error at the lein repl step: ~/hello-www> lein repl src/hello_www/core.clj Exception in thread "main" java.lang.IllegalArgumentExce...
Clojure vars and Java static methods
I'm a few days into learning Clojure and are having some teething problems, so I'm asking for advice. I'm trying to store a Java class in a Clojure var and call its static methods, but it doesn't work. Example: user=> (. java.lang.reflect.Modifier isPrivate 1) false user=> (def jmod java.lang.reflect.Modifier) #'user/jmod user=> (. j...
Clojure: Equivalent to Common Lisp READ function?
Hi there. When I want to read in an S-expression stored in a file into a running Common Lisp program, I do the following: (defun load-file (filename) "Loads data corresponding to a s-expression in file with name FILENAME." (with-open-file (stream filename) (read stream))) If, for example, I have a file named foo.txt that cont...
How can I define a clojure type that implements the servlet interface?
I'm attempting to use deftype (from the bleeding-edge clojure 1.2 branch) to create a java class that implements the java Servlet interface. I would expect the code below to compile (even though it's not very useful). (ns foo [:import [javax.servlet Servlet ServletRequest ServletResponse]]) (deftype servlet [] javax.servlet.Servle...
Using clojure.contrib functions in slime REPL
I want to use the functions in the clojure.contrib.trace namespace in slime at the REPL. How can I get slime to load them automatically? A related question, how can I add a specific namespace into a running repl? On the clojure.contrib API it describes usage like this: (ns my-namespace (:require clojure.contrib.trace)) But adding t...
Strange behaviour of keywords within macros in Clojure
I'm a little confused by how keyword accesses seem to behave in Clojure when they are evaluated at macro expansion time. The following works as I expect: (def m {:a 1}) (:a m) => 1 However the same keyword access doesn't seem to work within a macro: (def m {:a 1}) (defmacro get-a [x] (:a x)) (get-a m) => nil Any idea what is goin...