What advantage are Clojure's 1.4 reader literals, and why won't sample compile?
clojure
Solution
Reader literals let you create your own kinds of literals. Things like:
(< #meter 2 #inch 5)
(mass #molecule "H2O")
Unlike regular macros, reader literals are handled by the reader. So you can use them in s-expression based data files, not just code.
The literals are listed in `data_readers.clj` which must be at the root of your class path. That is in the `src` directory of a lein project.
Problem
I have two questions. First, what do I need to do to get the following code to compile, and what are the Clojure 1.4 reader literals giving me that I cannot get from macros? I understand I am overwriting the reader with the local data_readers.clj file, but where can I read further about these reader literals in more detail than in the Clojure 1.4 release notes, which I've already visited? Here is the code being compiled with error. ``` java.lang.RuntimeException: No reader function for tag ?=, ``` project.clj ``` (defproject repl-test "0.0.1-SNAPSHOT" :description "TODO: add summary of your project" :dependencies [[org.clojure/clojure "1.4.0"] [org.clojure/clojure-contrib "1.2.0"] [clojure-csv/clojure-csv "1.3.2"] [org.clojure/tools.cli "0.1.0"] [util "1.0.2-SNAPSHOT"] [clj-http "0.1.3"]] :aot [repl-test.core] :main repl-test.core) ``` data_readers.clj (located at the top of my lein project repl-test) ``` { ?= repl-test.core/debug-print str repl-test.core/expand-sexp } ``` Should data_readers.clj go somewhere else? If so, where? Pertinent parts of core.clj ``` (ns repl-test.core (:gen-class) (:require [clojure.string :as str]) (:require [util.core :as utl]) (:use clojure-csv.core)) (defn debug-print "Gauche debug print" [x] `(let [res# ~x] (println "?=" res#) res#)) (defn expand-sexp "Expand S-exp in string" [s] (let [ls (map-indexed #(if (even? %) %2 (read-string %2)) (str/split s #"`"))] `(apply str (list ~@ls)))) (defn -main [& args] (println (map inc #?=(range 10))) (let [i 100] (println #str"i = `i`") (println #str"(+ 1 2 3) = `(+ 1 2 3)`"))) ``` The example code came from here. Thanks.