using clojure.string causes WARNINGs

Question

When using clojure.string, I receive the following warnings

WARNING: replace already refers to: #'clojure.core/replace in namespace: tutorial.regexp, being replaced by: #'clojure.string/replace
WARNING: reverse already refers to: #'clojure.core/reverse in namespace: tutorial.regexp, being replaced by: #'clojure.string/reverse

my clojure script is:

(ns play-with-it
  (:use [clojure.string]))

Is there any way to fix those warnings?

Answer 1

Yes, switch to

(ns play-with-it
  (:require [clojure.string :as string]))

and then say e.g.

(string/replace ...)

to call clojure.string's replace function.

With :use, you bring in all Vars from clojure.string directly into your namespace, and since some of those have names clashing with Vars in clojure.core, you get the warning. Then you'd have to say clojure.core/replace to get at what's usually simply called replace.

The clash of names is by design; clojure.string is meant to be required with an alias like this. str and string are the most frequently chosen aliases.

Answer 2

In addition to Alex's answer you can also refer only the vars you want from a given namespace.

(ns foo.core
  (:use [clojure.string :only (replace-first)]))

This would not throw a warning since replace-first is not in clojure.core. However, you would still receive a warning if you did the following:

(ns foo.core
  (:use [clojure.string :only (replace)]))

In general it seems people are tending toward (ns foo.bar (:require [foo.bar :as baz])).

Answer 3

In addition to Michał's answer, you can exclude vars from clojure.core:

user=> (ns foo)
nil
foo=> (defn map [])
WARNING: map already refers to: #'clojure.core/map in namespace: foo, being replaced by: #'foo/map
#'foo/map
foo=> (ns bar
        (:refer-clojure :exclude [map]))
nil
bar=> (defn map [])
#'bar/map