Clojure:Lein跑不能解决符号

我刚开始使用lein开始我的第一个clojure项目,代码在这里:

(ns fileops.core
  (:use
    [clojure.core :only (slurp)]
    [clojure-csv.core :only (parse-csv)]
    [fileops.core]))

(defn -main
  "I don't do a whole lot ... yet."
  [& args]
  (read-file "sample.csv"))

(defn read-file
  "open and read the csv file"
  [fname]
  (with-open [file (clojure.java.io/reader fname)]
    (parse-csv (slurp fname))))

我尝试使用"lein run"运行它,但我一直收到此错误:

Caused by: java.lang.RuntimeException: Unable to resolve symbol: read-file in this context
    at clojure.lang.Util.runtimeException(Util.java:219)
    at clojure.lang.Compiler.resolveIn(Compiler.java:6874)
    at clojure.lang.Compiler.resolve(Compiler.java:6818)
    at clojure.lang.Compiler.analyzeSymbol(Compiler.java:6779)
    at clojure.lang.Compiler.analyze(Compiler.java:6343)
    ... 52 more

我究竟做错了什么？