:use fails in lein project

Question

When I try to use

   (ns eight-puzzle.core
      (:use [clojure.contrib.seq :only (positions)]))

I get this error

java.io.FileNotFoundException: Could not locate clojure/contrib/seq__init.class or        clojure/contrib/seq.clj on classpath: 
          RT.java:443 clojure.lang.RT.load
          RT.java:411 clojure.lang.RT.load
        core.clj:5530 clojure.core/load[fn]
        core.clj:5529 clojure.core/load
      RestFn.java:408 clojure.lang.RestFn.invoke
        core.clj:5336 clojure.core/load-one
        core.clj:5375 clojure.core/load-lib[fn]
        core.clj:5374 clojure.core/load-lib
      RestFn.java:142 clojure.lang.RestFn.applyTo
         core.clj:619 clojure.core/apply
        core.clj:5413 clojure.core/load-libs
      RestFn.java:137 clojure.lang.RestFn.applyTo
         core.clj:621 clojure.core/apply
        core.clj:5507 clojure.core/use
      RestFn.java:408 clojure.lang.RestFn.invoke
     NO_SOURCE_FILE:1 eight-puzzle.core/eval8699[fn]
     NO_SOURCE_FILE:1 eight-puzzle.core/eval8699

And this problem happens when ever I try to import anything in. Did I do something wrong when setting up clojure?

Answer 1

External dependencies, for projects managed by Leiningen, should be specified in the project.clj file, under the :dependencies key.

(defproject project1 "0.0.1"
  :description "Something"
  :dependencies [[org.clojure/clojure "1.5.1"]
                 [org.clojure/clojure-contrib "1.2.0"]
                 [clj-time "0.6.0"]])

Note: The entries in :dependencies can originate from either maven (maven central repository) or Clojars.

It also looks like you are using clojure.contrib. This library has been deprecated and you should upgrade, if you can. If you are only using clojure.contrib.seq/positions, take a look at this StackOverflow answer. You can also reimplement it with just clojure.core functions:

(defn positions [pred coll]
  (for [[idx elt]
        (map-indexed vector coll)
        :when (pred elt)]
    idx))