gistfile1.clj

(ns sample.grep
  "A simple complete Clojure program."
  (:use [clojure.contrib.io :only [read-lines]])
  (:gen-class))

(defn make-counter [initial-value]
  (let [current-value (atom initial-value)]
    (fn []
      (swap! current-value inc))))

(defn numbered-lines [lines]
  (let [cnt (make-counter 0)]
    (map #(vector (cnt) %) lines)))

(defn grep-in-file [pattern file]
  {file (filter #(re-find pattern (second %)) (numbered-lines (read-lines file)))})

(defn grep-in-files [pattern files]
  (apply merge (map #(grep-in-file pattern %) files)))

(defn print-matches [matches]
  (doseq [file-match matches]
    (let [fname (first file-match) 
	  matches (second file-match)]
      (doseq [match matches]
	(println (str fname ":" (first match) ":" (second match)))))))
	    
(defn -main [pattern & files]
  (if (or (nil? pattern) (empty? files))
    (println "Usage: grep <pattern> <file...>")
    (do 
      (println (format "grep started with pattern %s and file(s) %s" pattern (apply str (interpose ", " files))))
      (print-matches (grep-in-files (re-pattern pattern) files))
      (println "Done."))))