Clojure: How does (reader “/tmp/test.txt”) result in a BufferedReader

Question

I was trying to understand the following snippet of code.

use 'clojure.java.io)
(with-open [rdr (reader "/tmp/test.txt")]
  (doseq [line (line-seq rdr)]
    (println line)))

Though I can follow it at a reasonably level of fidelity I have trouble figuring out how (reader "/tmp/test.txt") result in a BufferedReader

When I search on reader and clojure I get this

In the same vane, is there a good treatment of Clojure IO -- the Java trails I read on Java IO were an excellent treatment of the subject. However I have had trouble finding a similarly succinct treatment of IO on Clojure. Unfortunately on Clojure one challenge has been that I find stuff in a very fragmented manner.

EDIT: As one of the posters has pointed out that the two readers are different -- I was aware of that -- the point I was trying to make was that I had a hard time finding the correct documentation for reader.

Answer 1

You mention two different kinds of readers in your post. The reader method is part of the java.io namespace, and you can check the clojure.java.io/reader API documentation to see what it does:

Usage: (reader x & opts) Attempts to coerce its argument into an open java.io.Reader. Default implementations always return a java.io.BufferedReader.

Default implementations are provided for Reader, BufferedReader, InputStream, File, URI, URL, Socket, byte arrays, character arrays, and String.

If argument is a String, it tries to resolve it first as a URI, then as a local file name. URIs with a 'file' protocol are converted to local file names.

Should be used inside with-open to ensure the Reader is properly closed.

The reader turned up by your Google search is Clojure's implementation of the Lisp reader . The Lisp reader is what parses Clojure syntax and lets you do dynamic things like read and eval at runtime.

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As for the second half of your question, I don't think there's a definitive source on I/O in Clojure. Since Clojure runs on the JVM and has full Java interop, I think your best bet is just reading through the Java Trails tutorial, then looking at the clojure.java.io API . For anything that's not nicely wrapped in the API you can either write your own wrappers, or just access the Java classes directly using Clojure syntax.