CODEWITHSUNDEEP
clojure
StillLearningToCode
StillLearningToCode

Reputation: 2461

including multiple files in a Clojure file

I am very new to Clojure. I know there is a way to include files in other files using a keyword like #include for C++. and i have done some digging and found a few things pointing to the keyword declare. Maybe I'm not using it correctly but it doesn't seem to work for me.

I am trying to write a function, for example, get_all_preds that uses another function predecessors, written in another file. the files are both under the directory src and each function is the only code in their respective files.

When i add (declare bar.clj) to the top of the foo.clj file i still get an error that bar cannot be found.

(defn get_all_preds
 ([tasks job]
   (cond (empty? (predecessors tasks job)) (println "No predecessors")
   :else (get_all_preds tasks (predecessors tasks job) (empty tasks))))
 ([tasks prereqs job]
   (cond (empty? prereqs) job
   :else (get_all_preds tasks (distinct (flatten (concat (predecessors tasks (first prereqs)) (rest prereqs)))) 
 (distinct (cons (first prereqs) job))))))

(defn predecessors
[tasks-list job]
  (cond (empty? tasks-list) 0
  (= job (first (first tasks-list))) (rest (rest (first tasks-list)))
  :else (predecessors (rest tasks-list) job)))

Upvotes: 0

Views: 1000

Answers (1)

noisesmith
noisesmith

Reputation: 20194

declare is for creating a var without binding it to a value.

The proper function for loading another Clojure namespace is require. To use require, you need to use namespaces, and create files with paths reflecting the semantic structure of the namespaces the files hold. The closest equivalent to #include is load, but this should be reserved for unstructured experiments where you might as well be copy / pasting into the repl, or unusual situations where namespaces are not appropriate.

A quick example:

in file src/foo/bar.clj:

(ns foo.bar)

(defn frob [] "hello")

in file src/foo/baz.clj:

(ns foo.baz
  (:require [foo.bar :as bar]))

(defn frob [] (str (bar/frob) (bar/frob)))

(defn -main [& args]
   (println (frob))

Running foo.baz/-main will print "hellohello" followed by a new line.

A Clojure namespace is a more structured concept than the compilation units of C, and is something that you can directly interact with in your code in a granular way. It will seem strange at first, but it allows fine grained control of what definitions are visible from various parts of your code (which in turn helps make code much easier to maintain and understand).

Upvotes: 3

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