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CLJ-1188 via Var intern
Signed-off-by: Stuart Halloway <[email protected]>
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‎src/jvm/clojure/api/API.java‎

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/**
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* Copyright (c) Rich Hickey and Contributors. All rights reserved.
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* The use and distribution terms for this software are covered by the
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* Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
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* which can be found in the file epl-v10.html at the root of this distribution.
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* By using this software in any fashion, you are agreeing to be bound by
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* the terms of this license.
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* You must not remove this notice, or any other, from this software.
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**/
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package clojure.api;
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import clojure.lang.IFn;
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import clojure.lang.Symbol;
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import clojure.lang.Var;
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public class API {
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private API() {}
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private static Symbol asSym(Object o) {
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Symbol s;
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if (o instanceof String) {
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s = Symbol.intern((String) o);
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} else {
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s = (Symbol) o;
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}
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return s;
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}
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/**
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* Returns the var associated with qualifiedName.
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*
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* @param qualifiedName a String or clojure.lang.Symbol
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* @return a clojure.lang.IFn
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*/
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public static IFn var(Object qualifiedName) {
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Symbol s = asSym(qualifiedName);
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return var(s.getNamespace(), s.getName());
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}
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/**
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* Returns an IFn associated with the namespace and name.
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*
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* @param ns a String or clojure.lang.Symbol
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* @param name a String or clojure.lang.Symbol
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* @return a clojure.lang.IFn
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*/
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public static IFn var(Object ns, Object name) {
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return Var.intern(asSym(ns), asSym(name));
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}
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/**
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* Read one object from the String s. Reads data in the
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* <a href="http://edn-format.org">edn format</a>.
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* @param s
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* @return an Object, or nil.
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*/
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public static Object read(String s) {
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return EDN_READ_STRING.invoke(s);
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}
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static {
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Symbol edn = (Symbol) var("clojure.core", "symbol").invoke("clojure.edn");
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var("clojure.core", "require").invoke(edn);
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}
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private static final IFn EDN_READ_STRING = var("clojure.edn", "read-string");
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}

‎src/jvm/clojure/api/package.html‎

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<html>
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<!--
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Copyright (c) Rich Hickey and Contributors. All rights reserved.
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The use and distribution terms for this software are covered by the
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Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
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which can be found in the file epl-v10.html at the root of this distribution.
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By using this software in any fashion, you are agreeing to be bound by
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the terms of this license.
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You must not remove this notice, or any other, from this software.
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-->
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<body>Clojure interop from Java.
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<p>The clojure.api package provides a minimal interface to bootstrap
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Clojure access from other JVM languages. It does this by providing:
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</p>
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<ol>
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<li>The ability to use Clojure's namespaces to locate an arbitrary
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<a href="http://clojure.org/vars">var</a>, returning the
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var's <code>clojure.lang.IFn</code> interface.</li>
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<li>A convenience method <code>read</code> for reading data using
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Clojure's edn reader</li>
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</ol>
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<p><code>IFn</code>s provide complete access to
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Clojure's <a href="http://clojure.github.com/clojure/">API</a>s.
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You can also access any other library written in Clojure, after adding
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either its source or compiled form to the classpath.</p>
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<p>The public Java API for Clojure consists of the following classes
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and interfaces:
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</p>
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<ol>
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<li>clojure.api.API</li>
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<li>clojure.lang.IFn</li>
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</ol>
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<p>All other Java classes should be treated as implementation details,
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and applications should avoid relying on them.</p>
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<p>To lookup and call a Clojure function:
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<pre>
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IFn plus = API.var("clojure.core", "+");
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plus.invoke(1, 2);
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</pre>
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</p>
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<p>Functions in <code>clojure.core</code> are automatically loaded. Other
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namespaces can be loaded via <code>require</code>:
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<pre>
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IFn require = API.var("clojure.core", "require");
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require.invoke(API.read("clojure.set"));
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</pre>
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</p>
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<p><code>IFn</code>s can be passed to higher order functions, e.g. the
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example below passes <code>plus</code> to <code>read</code>:
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<pre>
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IFn map = API.var("clojure.core", "map");
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IFn inc = API.var("clojure.core", "inc");
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map.invoke(inc, API.read("[1 2 3]"));
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</pre>
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</p>
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<p>Most IFns in Clojure refer to functions. A few, however, refer to
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non-function data values. To access these, use <code>deref</code>
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instead of <code>fn</code>:</p>
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<pre>
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IFn printLength = API.var("clojure.core", "*print-length*");
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API.var("clojure.core", "deref").invoke(printLength);
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</pre>
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</body>
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</html>

‎test/clojure/test_clojure/api.clj‎

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; Copyright (c) Rich Hickey. All rights reserved.
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; The use and distribution terms for this software are covered by the
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; Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
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; which can be found in the file epl-v10.html at the root of this distribution.
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; By using this software in any fashion, you are agreeing to be bound by
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; the terms of this license.
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; You must not remove this notice, or any other, from this software.
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(ns clojure.test-clojure.api
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(:require [clojure.test.generative :refer (defspec)]
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[clojure.test-clojure.generators :as cgen])
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(:import clojure.lang.IFn
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clojure.api.API
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clojure.lang.Var))
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(set! *warn-on-reflection* true)
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(defn roundtrip
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"Print an object and read it back with API/read"
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[o]
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(binding [*print-length* nil
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*print-dup* nil
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*print-level* nil]
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(API/read (pr-str o))))
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(defn api-var-str
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[^Var v]
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(API/var (str (.name (.ns v)))
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(str (.sym v))))
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(defn api-var
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[^Var v]
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(API/var (.name (.ns v))
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(.sym v)))
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(defspec api-can-read
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roundtrip
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[^{:tag cgen/ednable} o]
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(when-not (= o %)
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(throw (ex-info "Value cannot roundtrip with API/read" {:printed o :read %}))))
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(defspec api-can-find-var
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api-var
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[^{:tag cgen/var} v]
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(when-not (= v %)
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(throw (ex-info "Var cannot roundtrip through API/var" {:from v :to %}))))
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(defspec api-can-find-var-str
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api-var-str
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[^{:tag cgen/var} v]
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(when-not (= v %)
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(throw (ex-info "Var cannot roundtrip strings through API/var" {:from v :to %}))))
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