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Clojure Interoperability

This document discusses interoperability between Clojure and Python. It outlines Jython, which allows Python code to run on the Java Virtual Machine (JVM), and Clojure, a Lisp dialect that also runs on the JVM. It then covers how Clojure and Jython code can interact and call each other due to both running on the JVM. It provides examples of implementing Python objects in Clojure and calling Jython functions from Clojure.

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INTEROPERABILITY CLOJURE PYTHON Enrico Franchi
2 OUTLINE Why Clojure? Why Java? Clojure from 3000 m. Jython-Clojure interoperability Clojure-Jython interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
3 GENERAL NOTES During this presentation some very explicit Java code may be shown. No ducks were harmed during the making of this presentation. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
4 JVM LANGUAGES Jython Java ? JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
5 JVM LANGUAGES Jython Java Clojure JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
6 CLOJURE Clojure is Lisp Clojure is a good Lisp Clojure has a more functional flavor than Common Lisp; stateful programming is banned unless in very controlled ways Clojure lives on the JVM and perhaps its rejection of state is a reaction to the heavily stateful model of JVM Clojure is not a pure functional language by any means ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
7 JVM LANGUAGES Jython Implementation of Python in Java Jython calls Java ~ Clojure New Programming Languages built on the JVM Design choices in Clojure reflect design choices of the JVM Interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
8 CLOJURE ~ Good Parts ~ Functional Programming Laziness Full Macros Multi-Methods Immutable types, STM & Concurrency Model ~ Bad Parts ~ “Java” ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
9 ATOMIC TYPES Integers Floating Point Numbers Ratios (3/4 is not 0.75, is ¾) BigDecimal Strings (“foo”) Booleans (true, false) Nil (nil) Characters (a, b) :keywords regexp’s (#“foo.*”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
10 SEQUENCE TYPES Python Common Lisp Clojure Type Syntax Type Syntax Type Syntax Random access list [1, 2] vector #(1 2) vector [1 2] sequence Linked List - No list (1 2) list (1 2) Set set {1, 2} No No set #{1 2} Map dict {1:2, 3:4} hash-table No vector {1 2, 3 4} Clojure collections In Clojure all collections are immutable; implement corresponding all the functions return a new collections – as usual, Java collections interfaces immutability allows easy data sharing – vector, list List set Set map Map ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
11 CLOJURE EXAMPLE (defn rember [a lat]   (cond    (empty? lat) '()    (= (first lat) a) (rest lat)    :else (cons           (first lat)           (rember a (rest lat))))) (rember 4 '(1 2 3 4 5 6 4)) ; => (1 2 3 5 6 4) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
12 TAIL CALL OPTIMIZATION (defn multirember [a lat]   (letfn       [(multirember-aux [source sink]                    (if (seq source)                      (if (= (first source) a)                        (recur (rest source) sink)                        (recur (rest source)                               (conj sink (first source))))                      sink))]     (multirember-aux lat []))) (take 10 (multirember 4 '(1 2 3 4 5 6 4)) (multirember 4 (iterate inc 0))) ; => [1 2 3 5 6] ; Evaluation aborted. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
13 LAZINESS (defn lazy-multirember [a lat]   (letfn       [(multirember-aux [source]                         (lazy-seq                          (if (seq source)                            (if (= (first source) a)                              (multirember-aux (rest source))                              (cons (first source)                                    (multirember-aux (rest source))))                           '())))]     (multirember-aux lat))) (take 10 (lazy-multirember 4 (iterate inc 0))) ; => (0 1 2 3 5 6 7 8 9 10)
14 NAMESPACES & MODULES (ns example.namespace) (ns example.namespace (:require clojure.set)) Introduces a new namespace. With def (and defn, …) stuff is (ns example.namespace added to namespaces. (:require [clojure.set :as s])) (ns example.namespace (ns example.namespace (:use clojure.string)) (:import [java.util HashMap])) (ns example.namespace (:use [clojure.string :only [capitalize]])) (ns example.namespace (:use [clojure.string :exclude [capitalize]]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
15 CALLING JAVA Java Clojure Jython import app.model.Person; (import [app.model Person]) from app.model import Person new Person() (new Person) Person() (Person.) person.getFullName() (. getFullName person) person.getFullName() (.getFullName person) Locale.JAPAN (. Locale JAPAN) Locale.JAPAN Locale/JAPAN Integer.valueOf(“42”) (. Integer valueOf "42") java.lang.Integer.valueOf('42') (Integer/valueOf “42”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
16 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton] (gui-sample/build-gui            [java.awt.event ActionListener])) "Rock & Roll" (defn build-gui [title message] "Hello, world!”)   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button                         (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message))))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
17 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton]            [java.awt.event ActionListener])) (defn build-gui [title message]   (let [frame (JFrame. title)         button (JButton. "CLICK")         px (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message)))]     (.addActionListener button px)     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true) px))      (update-proxy p {"actionPerformed" (fn [this evt] (println "foo!"))}) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
18 GEN-CLASS (ns example.ClassExample   (:gen-class    :name example.ClassExample    :extends Object    :implements []    :methods [ [foo [java.util.Collection] int]              ^{:static true} [show [java.util.Collection] void]])   (:import (java.util Collection))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
19 GEN-CLASS (2) (defn show [coll] (defn -show [coll]   (if (seq coll)   (show coll))     (do       (print (first coll)) (defn -foo [this coll]       (recur (rest coll)))   (let [coll (seq coll)]     (println "")))     (if coll (count coll) -1))) >>> import example >>> example.ClassExample.show([1, 2, 3]) 123 >>> ce = example.ClassExample() >>> ce.foo([1, 2, 3]) 3
20 IMPLEMENTING PYOBJECTS IN CLOJURE import clj (ns clj.ImmutableList (:gen-class py_list = ['a', 'b', 'c'] :name clj.ImmutableList my_list = clj.ImmutableList(py_list) :extends org.python.core.PyObject :implements [clojure.lang.IPersistentList] :state state :init init :constructors {[java.util.Collection], []}) (:import [org.python.core PyObject PyInteger Py])) (defn -init [coll] [[coll] (apply list coll)]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
21 IMPLEMENTING PYOBJECTS IN CLOJURE (2) (defmacro delegate-to-state [sym] (defn -cons [this other] `(defn ~(symbol (str "-" sym)) (cons (.state this) other)) [this#] (~sym (.state this#)))) (defn -equiv [this other] print(.state this) other)) (= my_list.peek() (delegate-to-state peek) print my_list.pop() (delegate-to-state pop) print my_list.count() (delegate-to-state count) print my_list.empty() (delegate-to-state empty) print my_list.seq() (delegate-to-state seq) print my_list.cons('d') print my_list.equiv(py_list) print my_list.equiv(['a', 'b', 'c']) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
22 IMPLEMENTING PYOBJECTS print my_list[0] IN CLOJURE (3) print my_list[1] print my_list[2] (defn -__finditem__ [this index] print my_list[2.4] (let [index (if (instance? Number index) index try: (Py/tojava index Number))] print my_list[3] except IndexError, e: (try print e (Py/java2py (nth (.state this) index)) try: (catch IndexOutOfBoundsException e print my_list['a'] (throw (Py/IndexError (.toString e))))))) except TypeError, e: print e try: my_list[0] = 1 except TypeError, e: print e ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
23 CLOJURE RT from clojure.lang import RT, Compiler source = ''' (ns rember) Compiler.load(java.io.StringReader(source)) (defn rember [a lat] rember = RT.var('rember', 'rember') (cond print rember.invoke(2, range(4)) (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat))))) ''' ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
24 CLOJURE DECORATOR import pyclj @pyclj.clojure def rember(a, lat):     ’’’(defn rember "Remove first occurrence of a from lat" [a lat] (cond (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat)))))’’’ if __name__ == '__main__':     print rember(2, range(4))     help(rember) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
25 IMPLEMENTATION def clojure(fn):     """Decorator that substitutes an empty python function with clojure in the doc with a callable which delegates to the clojure function. """     clj_namespace = determine_clojure_namespace(fn)     clojure_fnc = build_clojure_function_object(clj_namespace, fn)     fn.__doc__ = get_docs(clojure_fnc)     def aux(*args):         return clojure_fnc.invoke(*args)     functools.update_wrapper(aux, fn)     return aux ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
26 IMPLEMENTATION (2) def determine_clojure_namespace(fn):     try:         clj_namespace = fn.__module__     except AttributeError:         clj_namespace = 'user'     return clj_namespace def get_docs(clojure_fnc):     meta = clojure_fnc.meta()     return meta.get(Keyword.intern('doc')) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
27 IMPLEMENTATION (3) def build_clojure_function_object(clj_namespace, fn):     clojure_code = '(ns %s)n%s' % (         clj_namespace,         fn.__doc__)     clojure_compile_string(clojure_code)     clojure_fnc = RT.var(clj_namespace, fn.func_name)     return clojure_fnc ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
28 CALLING JYTHON FROM CLOJURE (defn make-factory [modulename klassname]   (let [interpreter (PythonInterpreter.) class SpamAndEggs(object):          import-command (str-join " " ["from" modulename     def __init__(self, eggs): "import" klassname])]         self.eggs = eggs     (.exec interpreter import-command)     (.get interpreter klassname))) hasSpam(self):     def         return True (def spam-and-eggs (make-factory "example" "SpamAndEggs"))     def getEggs(self): (def inst (.__call__ spam-and-eggs (Py/java2py 1)))         return self.eggs (println inst)     def __repr__(self): (println (.invoke inst "hasSpam"))         return 'Spam and %s eggs.' % self.eggs
29 CALLING JYTHON FROM CLOJURE (PT. 2) (defn make-factory   [module klassname]   (let [interpreter (PythonInterpreter.)         import-command (str-join " " ["from" module "import" klassname])]     (.exec interpreter import-command)     (let [klass (.get interpreter klassname)]       (fn [& args]         (.__call__ klass           (into-array PyObject             (map #(Py/java2py %) args))))))) (def spam-and-eggs (make-factory "example" "SpamAndEggs")) (def inst (spam-and-eggs 1))
30 THROW MACROS IN (defmacro pyclass [q-class jtype]   (let [[klass-name module-name] (split-module-and-class q-class)]     `(def ~(symbol klass-name)       (make-factory ~(str module-name) ~(str klass-name) ~jtype)))) (pyclass example.PrintSomething java.awt.event.ActionListener) (def evt-printer (PrintSomething)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
31 MAKE-FACTORY (AGAIN) (defn make-factory [module klassname interface] (let [interpreter (PythonInterpreter.) import-command (str-join " " ["from" module "import" klassname])] (.exec interpreter import-command) (let [klass (.get interpreter klassname)] (fn [& args] (.__tojava__ (.__call__ klass (into-array PyObject (map #(Py/java2py %) args))) interface))))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
32 BACK TO THE BEGINNING (defn build-gui [title]   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button (PrintSomething))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
33 CONCLUSION Thanks for Your Kind Attention https://github.com/rik0/PyCLJ_Examples https://github.com/rik0/pyclj ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
INTEROPERABILITY CLOJURE PYTHON Enrico Franchi
35 OUTLINE Why Clojure? Why Java? Clojure from 3000 m. Jython-Clojure interoperability Clojure-Jython interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
36 GENERAL NOTES During this presentation some very explicit Java code may be shown. No ducks were harmed during the making of this presentation. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
37 GENERAL NOTES During this presentation some very explicit Java code may be shown. No ducks were harmed during the making of this presentation. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
38 JVM LANGUAGES Jython Java ? JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
39 JVM LANGUAGES Jython Java Clojure JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
40 CLOJURE Clojure is Lisp Clojure is a good Lisp Clojure has a more functional flavor than Common Lisp; stateful programming is banned unless in very controlled ways Clojure lives on the JVM and perhaps its rejection of state is a reaction to the heavily stateful model of JVM Clojure is not a pure functional language by any means ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
41 JVM LANGUAGES Jython Implementation of Python in Java Jython calls Java ~ Clojure New Programming Languages built on the JVM Design choices in Clojure reflect design choices of the JVM Interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
42 CLOJURE ~ Good Parts ~ Functional Programming Laziness Full Macros Multi-Methods Immutable types, STM & Concurrency Model ~ Bad Parts ~ “Java” ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
43 ATOMIC TYPES Integers Floating Point Numbers Ratios (3/4 is not 0.75, is ¾) BigDecimal Strings (“foo”) Booleans (true, false) Nil (nil) Characters (a, b) :keywords regexp’s (#“foo.*”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
44 SEQUENCE TYPES Python Common Lisp Clojure Type Syntax Type Syntax Type Syntax Random access list [1, 2] vector #(1 2) vector [1 2] sequence Linked List - No list (1 2) list (1 2) Set set {1, 2} No No set #{1 2} Map dict {1:2, 3:4} hash-table No vector {1 2, 3 4} Clojure collections In Clojure all collections are immutable; implement corresponding all the functions return a new collections – as usual, Java collections interfaces immutability allows easy data sharing – vector, list List set Set map Map ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
45 CLOJURE EXAMPLE (defn rember [a lat]   (cond    (empty? lat) '()    (= (first lat) a) (rest lat)    :else (cons           (first lat)           (rember a (rest lat))))) (rember 4 '(1 2 3 4 5 6 4)) ; => (1 2 3 5 6 4) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
46 TAIL CALL OPTIMIZATION (defn multirember [a lat]   (letfn       [(multirember-aux [source sink]                    (if (seq source)                      (if (= (first source) a)                        (recur (rest source) sink)                        (recur (rest source)                               (conj sink (first source))))                      sink))]     (multirember-aux lat []))) (take 10 (multirember 4 '(1 2 3 4 5 6 4)) (multirember 4 (iterate inc 0))) ; => [1 2 3 5 6] ; Evaluation aborted. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
47 LAZINESS (defn lazy-multirember [a lat]   (letfn       [(multirember-aux [source]                         (lazy-seq                          (if (seq source)                            (if (= (first source) a)                              (multirember-aux (rest source))                              (cons (first source)                                    (multirember-aux (rest source))))                           '())))]     (multirember-aux lat))) (take 10 (lazy-multirember 4 (iterate inc 0))) ; => (0 1 2 3 5 6 7 8 9 10)
48 NAMESPACES & MODULES (ns example.namespace) (ns example.namespace (:require clojure.set)) Introduces a new namespace. With def (and defn, …) stuff is (ns example.namespace added to namespaces. (:require [clojure.set :as s])) (ns example.namespace (ns example.namespace (:use clojure.string)) (:import [java.util HashMap])) (ns example.namespace (:use [clojure.string :only [capitalize]])) (ns example.namespace (:use [clojure.string :exclude [capitalize]]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
49 CALLING JAVA Java Clojure Jython import app.model.Person; (import [app.model Person]) from app.model import Person new Person() (new Person) Person() (Person.) person.getFullName() (. getFullName person) person.getFullName() (.getFullName person) Locale.JAPAN (. Locale JAPAN) Locale.JAPAN Locale/JAPAN Integer.valueOf(“42”) (. Integer valueOf "42") java.lang.Integer.valueOf('42') (Integer/valueOf “42”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
50 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton] (gui-sample/build-gui            [java.awt.event ActionListener])) "Rock & Roll" (defn build-gui [title message] "Hello, world!”)   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button                         (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message))))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
51 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton]            [java.awt.event ActionListener])) (defn build-gui [title message]   (let [frame (JFrame. title)         button (JButton. "CLICK")         px (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message)))]     (.addActionListener button px)     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true) px))      (update-proxy p {"actionPerformed" (fn [this evt] (println "foo!"))}) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
52 GEN-CLASS (ns example.ClassExample   (:gen-class    :name example.ClassExample    :extends Object    :implements []    :methods [ [foo [java.util.Collection] int]              ^{:static true} [show [java.util.Collection] void]])   (:import (java.util Collection))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
53 GEN-CLASS (2) (defn show [coll] (defn -show [coll]   (if (seq coll)   (show coll))     (do       (print (first coll)) (defn -foo [this coll]       (recur (rest coll)))   (let [coll (seq coll)]     (println "")))     (if coll (count coll) -1))) >>> import example >>> example.ClassExample.show([1, 2, 3]) 123 >>> ce = example.ClassExample() >>> ce.foo([1, 2, 3]) 3
54 IMPLEMENTING PYOBJECTS IN CLOJURE (ns clj.ImmutableList (:gen-class :name clj.ImmutableList :extends org.python.core.PyObject :implements [clojure.lang.IPersistentList] :state state :init init :constructors {[java.util.Collection], []}) (:import [org.python.core PyObject PyInteger Py])) (defn -init [coll] [[coll] (apply list coll)]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
55 IMPLEMENTING PYOBJECTS IN CLOJURE import clj (ns clj.ImmutableList (:gen-class py_list = ['a', 'b', 'c'] :name clj.ImmutableList my_list = clj.ImmutableList(py_list) :extends org.python.core.PyObject :implements [clojure.lang.IPersistentList] :state state :init init :constructors {[java.util.Collection], []}) (:import [org.python.core PyObject PyInteger Py])) (defn -init [coll] [[coll] (apply list coll)]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
56 IMPLEMENTING PYOBJECTS IN CLOJURE (2) (defmacro delegate-to-state [sym] (defn -cons [this other] `(defn ~(symbol (str "-" sym)) (cons (.state this) other)) [this#] (~sym (.state this#)))) (defn -equiv [this other] (= (.state this) other)) (delegate-to-state peek) (delegate-to-state pop) (delegate-to-state count) (delegate-to-state empty) (delegate-to-state seq) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
57 IMPLEMENTING PYOBJECTS IN CLOJURE (2) (defmacro delegate-to-state [sym] (defn -cons [this other] `(defn ~(symbol (str "-" sym)) (cons (.state this) other)) [this#] (~sym (.state this#)))) (defn -equiv [this other] print(.state this) other)) (= my_list.peek() (delegate-to-state peek) print my_list.pop() (delegate-to-state pop) print my_list.count() (delegate-to-state count) print my_list.empty() (delegate-to-state empty) print my_list.seq() (delegate-to-state seq) print my_list.cons('d') print my_list.equiv(py_list) print my_list.equiv(['a', 'b', 'c']) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
58 IMPLEMENTING PYOBJECTS print my_list[0] IN CLOJURE (3) print my_list[1] print my_list[2] (defn -__finditem__ [this index] print my_list[2.4] (let [index (if (instance? Number index) index try: (Py/tojava index Number))] print my_list[3] except IndexError, e: (try print e (Py/java2py (nth (.state this) index)) try: (catch IndexOutOfBoundsException e print my_list['a'] (throw (Py/IndexError (.toString e))))))) except TypeError, e: print e try: my_list[0] = 1 except TypeError, e: print e ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
59 CLOJURE RT from clojure.lang import RT, Compiler source = ''' (ns rember) Compiler.load(java.io.StringReader(source)) (defn rember [a lat] rember = RT.var('rember', 'rember') (cond print rember.invoke(2, range(4)) (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat))))) ''' ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
60 CLOJURE DECORATOR import pyclj @pyclj.clojure def rember(a, lat):     ’’’(defn rember "Remove first occurrence of a from lat" [a lat] (cond (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat)))))’’’ if __name__ == '__main__':     print rember(2, range(4))     help(rember) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
61 IMPLEMENTATION def clojure(fn):     """Decorator that substitutes an empty python function with clojure in the doc with a callable which delegates to the clojure function. """     clj_namespace = determine_clojure_namespace(fn)     clojure_fnc = build_clojure_function_object(clj_namespace, fn)     fn.__doc__ = get_docs(clojure_fnc)     def aux(*args):         return clojure_fnc.invoke(*args)     functools.update_wrapper(aux, fn)     return aux ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
62 IMPLEMENTATION (2) def determine_clojure_namespace(fn):     try:         clj_namespace = fn.__module__     except AttributeError:         clj_namespace = 'user'     return clj_namespace def get_docs(clojure_fnc):     meta = clojure_fnc.meta()     return meta.get(Keyword.intern('doc')) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
63 IMPLEMENTATION (3) def build_clojure_function_object(clj_namespace, fn):     clojure_code = '(ns %s)n%s' % (         clj_namespace,         fn.__doc__)     clojure_compile_string(clojure_code)     clojure_fnc = RT.var(clj_namespace, fn.func_name)     return clojure_fnc ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
64 CALLING JYTHON FROM CLOJURE (defn make-factory [modulename klassname]   (let [interpreter (PythonInterpreter.)          import-command (str-join " " ["from" modulename "import" klassname])]     (.exec interpreter import-command)     (.get interpreter klassname))) (def spam-and-eggs (make-factory "example" "SpamAndEggs")) (def inst (.__call__ spam-and-eggs (Py/java2py 1))) (println inst) (println (.invoke inst "hasSpam"))
65 CALLING JYTHON FROM CLOJURE (defn make-factory [modulename klassname]   (let [interpreter (PythonInterpreter.) class SpamAndEggs(object):          import-command (str-join " " ["from" modulename     def __init__(self, eggs): "import" klassname])]         self.eggs = eggs     (.exec interpreter import-command)     (.get interpreter klassname))) hasSpam(self):     def         return True (def spam-and-eggs (make-factory "example" "SpamAndEggs"))     def getEggs(self): (def inst (.__call__ spam-and-eggs (Py/java2py 1)))         return self.eggs (println inst)     def __repr__(self): (println (.invoke inst "hasSpam"))         return 'Spam and %s eggs.' % self.eggs
66 CALLING JYTHON FROM CLOJURE (PT. 2) (defn make-factory   [module klassname]   (let [interpreter (PythonInterpreter.)         import-command (str-join " " ["from" module "import" klassname])]     (.exec interpreter import-command)     (let [klass (.get interpreter klassname)]       (fn [& args]         (.__call__ klass           (into-array PyObject             (map #(Py/java2py %) args))))))) (def spam-and-eggs (make-factory "example" "SpamAndEggs")) (def inst (spam-and-eggs 1))
67 THROW MACROS IN (defmacro pyclass [q-class jtype]   (let [[klass-name module-name] (split-module-and-class q-class)]     `(def ~(symbol klass-name)       (make-factory ~(str module-name) ~(str klass-name) ~jtype)))) (pyclass example.PrintSomething java.awt.event.ActionListener) (def evt-printer (PrintSomething)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
68 MAKE-FACTORY (AGAIN) (defn make-factory [module klassname interface] (let [interpreter (PythonInterpreter.) import-command (str-join " " ["from" module "import" klassname])] (.exec interpreter import-command) (let [klass (.get interpreter klassname)] (fn [& args] (.__tojava__ (.__call__ klass (into-array PyObject (map #(Py/java2py %) args))) interface))))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
69 BACK TO THE BEGINNING (defn build-gui [title]   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button (PrintSomething))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
70 CONCLUSION Thanks for Your Kind Attention https://github.com/rik0/PyCLJ_Examples https://github.com/rik0/pyclj ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>

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Clojure Interoperability

  • 1.
    INTEROPERABILITY CLOJURE PYTHON Enrico Franchi
  • 2.
    2 OUTLINE Why Clojure? Why Java? Clojure from 3000 m. Jython-Clojure interoperability Clojure-Jython interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 3.
    3 GENERAL NOTES During this presentation some very explicit Java code may be shown. No ducks were harmed during the making of this presentation. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 4.
    4 JVM LANGUAGES Jython Java ? JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 5.
    5 JVM LANGUAGES Jython Java Clojure JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 6.
    6 CLOJURE Clojure is Lisp Clojure is a good Lisp Clojure has a more functional flavor than Common Lisp; stateful programming is banned unless in very controlled ways Clojure lives on the JVM and perhaps its rejection of state is a reaction to the heavily stateful model of JVM Clojure is not a pure functional language by any means ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 7.
    7 JVM LANGUAGES Jython Implementation of Python in Java Jython calls Java ~ Clojure New Programming Languages built on the JVM Design choices in Clojure reflect design choices of the JVM Interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 8.
    8 CLOJURE ~ Good Parts ~ Functional Programming Laziness Full Macros Multi-Methods Immutable types, STM & Concurrency Model ~ Bad Parts ~ “Java” ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 9.
    9 ATOMIC TYPES Integers Floating Point Numbers Ratios (3/4 is not 0.75, is ¾) BigDecimal Strings (“foo”) Booleans (true, false) Nil (nil) Characters (a, b) :keywords regexp’s (#“foo.*”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 10.
    10 SEQUENCE TYPES Python Common Lisp Clojure Type Syntax Type Syntax Type Syntax Random access list [1, 2] vector #(1 2) vector [1 2] sequence Linked List - No list (1 2) list (1 2) Set set {1, 2} No No set #{1 2} Map dict {1:2, 3:4} hash-table No vector {1 2, 3 4} Clojure collections In Clojure all collections are immutable; implement corresponding all the functions return a new collections – as usual, Java collections interfaces immutability allows easy data sharing – vector, list List set Set map Map ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 11.
    11 CLOJURE EXAMPLE (defn rember [a lat]   (cond    (empty? lat) '()    (= (first lat) a) (rest lat)    :else (cons           (first lat)           (rember a (rest lat))))) (rember 4 '(1 2 3 4 5 6 4)) ; => (1 2 3 5 6 4) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 12.
    12 TAIL CALL OPTIMIZATION (defn multirember [a lat]   (letfn       [(multirember-aux [source sink]                    (if (seq source)                      (if (= (first source) a)                        (recur (rest source) sink)                        (recur (rest source)                               (conj sink (first source))))                      sink))]     (multirember-aux lat []))) (take 10 (multirember 4 '(1 2 3 4 5 6 4)) (multirember 4 (iterate inc 0))) ; => [1 2 3 5 6] ; Evaluation aborted. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 13.
    13 LAZINESS (defn lazy-multirember [a lat]   (letfn       [(multirember-aux [source]                         (lazy-seq                          (if (seq source)                            (if (= (first source) a)                              (multirember-aux (rest source))                              (cons (first source)                                    (multirember-aux (rest source))))                           '())))]     (multirember-aux lat))) (take 10 (lazy-multirember 4 (iterate inc 0))) ; => (0 1 2 3 5 6 7 8 9 10)
  • 14.
    14 NAMESPACES & MODULES (ns example.namespace) (ns example.namespace (:require clojure.set)) Introduces a new namespace. With def (and defn, …) stuff is (ns example.namespace added to namespaces. (:require [clojure.set :as s])) (ns example.namespace (ns example.namespace (:use clojure.string)) (:import [java.util HashMap])) (ns example.namespace (:use [clojure.string :only [capitalize]])) (ns example.namespace (:use [clojure.string :exclude [capitalize]]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 15.
    15 CALLING JAVA Java Clojure Jython import app.model.Person; (import [app.model Person]) from app.model import Person new Person() (new Person) Person() (Person.) person.getFullName() (. getFullName person) person.getFullName() (.getFullName person) Locale.JAPAN (. Locale JAPAN) Locale.JAPAN Locale/JAPAN Integer.valueOf(“42”) (. Integer valueOf "42") java.lang.Integer.valueOf('42') (Integer/valueOf “42”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 16.
    16 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton] (gui-sample/build-gui            [java.awt.event ActionListener])) "Rock & Roll" (defn build-gui [title message] "Hello, world!”)   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button                         (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message))))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 17.
    17 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton]            [java.awt.event ActionListener])) (defn build-gui [title message]   (let [frame (JFrame. title)         button (JButton. "CLICK")         px (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message)))]     (.addActionListener button px)     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true) px))      (update-proxy p {"actionPerformed" (fn [this evt] (println "foo!"))}) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 18.
    18 GEN-CLASS (ns example.ClassExample   (:gen-class    :name example.ClassExample    :extends Object    :implements []    :methods [ [foo [java.util.Collection] int]              ^{:static true} [show [java.util.Collection] void]])   (:import (java.util Collection))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 19.
    19 GEN-CLASS (2) (defn show [coll] (defn -show [coll]   (if (seq coll)   (show coll))     (do       (print (first coll)) (defn -foo [this coll]       (recur (rest coll)))   (let [coll (seq coll)]     (println "")))     (if coll (count coll) -1))) >>> import example >>> example.ClassExample.show([1, 2, 3]) 123 >>> ce = example.ClassExample() >>> ce.foo([1, 2, 3]) 3
  • 20.
    20 IMPLEMENTING PYOBJECTS IN CLOJURE import clj (ns clj.ImmutableList (:gen-class py_list = ['a', 'b', 'c'] :name clj.ImmutableList my_list = clj.ImmutableList(py_list) :extends org.python.core.PyObject :implements [clojure.lang.IPersistentList] :state state :init init :constructors {[java.util.Collection], []}) (:import [org.python.core PyObject PyInteger Py])) (defn -init [coll] [[coll] (apply list coll)]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 21.
    21 IMPLEMENTING PYOBJECTS IN CLOJURE (2) (defmacro delegate-to-state [sym] (defn -cons [this other] `(defn ~(symbol (str "-" sym)) (cons (.state this) other)) [this#] (~sym (.state this#)))) (defn -equiv [this other] print(.state this) other)) (= my_list.peek() (delegate-to-state peek) print my_list.pop() (delegate-to-state pop) print my_list.count() (delegate-to-state count) print my_list.empty() (delegate-to-state empty) print my_list.seq() (delegate-to-state seq) print my_list.cons('d') print my_list.equiv(py_list) print my_list.equiv(['a', 'b', 'c']) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 22.
    22 IMPLEMENTING PYOBJECTS print my_list[0] IN CLOJURE (3) print my_list[1] print my_list[2] (defn -__finditem__ [this index] print my_list[2.4] (let [index (if (instance? Number index) index try: (Py/tojava index Number))] print my_list[3] except IndexError, e: (try print e (Py/java2py (nth (.state this) index)) try: (catch IndexOutOfBoundsException e print my_list['a'] (throw (Py/IndexError (.toString e))))))) except TypeError, e: print e try: my_list[0] = 1 except TypeError, e: print e ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 23.
    23 CLOJURE RT from clojure.lang import RT, Compiler source = ''' (ns rember) Compiler.load(java.io.StringReader(source)) (defn rember [a lat] rember = RT.var('rember', 'rember') (cond print rember.invoke(2, range(4)) (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat))))) ''' ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 24.
    24 CLOJURE DECORATOR import pyclj @pyclj.clojure def rember(a, lat):     ’’’(defn rember "Remove first occurrence of a from lat" [a lat] (cond (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat)))))’’’ if __name__ == '__main__':     print rember(2, range(4))     help(rember) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 25.
    25 IMPLEMENTATION def clojure(fn):     """Decorator that substitutes an empty python function with clojure in the doc with a callable which delegates to the clojure function. """     clj_namespace = determine_clojure_namespace(fn)     clojure_fnc = build_clojure_function_object(clj_namespace, fn)     fn.__doc__ = get_docs(clojure_fnc)     def aux(*args):         return clojure_fnc.invoke(*args)     functools.update_wrapper(aux, fn)     return aux ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 26.
    26 IMPLEMENTATION (2) def determine_clojure_namespace(fn):     try:         clj_namespace = fn.__module__     except AttributeError:         clj_namespace = 'user'     return clj_namespace def get_docs(clojure_fnc):     meta = clojure_fnc.meta()     return meta.get(Keyword.intern('doc')) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 27.
    27 IMPLEMENTATION (3) def build_clojure_function_object(clj_namespace, fn):     clojure_code = '(ns %s)n%s' % (         clj_namespace,         fn.__doc__)     clojure_compile_string(clojure_code)     clojure_fnc = RT.var(clj_namespace, fn.func_name)     return clojure_fnc ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 28.
    28 CALLING JYTHON FROM CLOJURE (defn make-factory [modulename klassname]   (let [interpreter (PythonInterpreter.) class SpamAndEggs(object):          import-command (str-join " " ["from" modulename     def __init__(self, eggs): "import" klassname])]         self.eggs = eggs     (.exec interpreter import-command)     (.get interpreter klassname))) hasSpam(self):     def         return True (def spam-and-eggs (make-factory "example" "SpamAndEggs"))     def getEggs(self): (def inst (.__call__ spam-and-eggs (Py/java2py 1)))         return self.eggs (println inst)     def __repr__(self): (println (.invoke inst "hasSpam"))         return 'Spam and %s eggs.' % self.eggs
  • 29.
    29 CALLING JYTHON FROM CLOJURE (PT. 2) (defn make-factory   [module klassname]   (let [interpreter (PythonInterpreter.)         import-command (str-join " " ["from" module "import" klassname])]     (.exec interpreter import-command)     (let [klass (.get interpreter klassname)]       (fn [& args]         (.__call__ klass           (into-array PyObject             (map #(Py/java2py %) args))))))) (def spam-and-eggs (make-factory "example" "SpamAndEggs")) (def inst (spam-and-eggs 1))
  • 30.
    30 THROW MACROS IN (defmacro pyclass [q-class jtype]   (let [[klass-name module-name] (split-module-and-class q-class)]     `(def ~(symbol klass-name)       (make-factory ~(str module-name) ~(str klass-name) ~jtype)))) (pyclass example.PrintSomething java.awt.event.ActionListener) (def evt-printer (PrintSomething)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 31.
    31 MAKE-FACTORY (AGAIN) (defn make-factory [module klassname interface] (let [interpreter (PythonInterpreter.) import-command (str-join " " ["from" module "import" klassname])] (.exec interpreter import-command) (let [klass (.get interpreter klassname)] (fn [& args] (.__tojava__ (.__call__ klass (into-array PyObject (map #(Py/java2py %) args))) interface))))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 32.
    32 BACK TO THE BEGINNING (defn build-gui [title]   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button (PrintSomething))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 33.
    33 CONCLUSION Thanks for Your Kind Attention https://github.com/rik0/PyCLJ_Examples https://github.com/rik0/pyclj ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 34.
    INTEROPERABILITY CLOJURE PYTHON Enrico Franchi
  • 35.
    35 OUTLINE Why Clojure? Why Java? Clojure from 3000 m. Jython-Clojure interoperability Clojure-Jython interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 36.
    36 GENERAL NOTES During this presentation some very explicit Java code may be shown. No ducks were harmed during the making of this presentation. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 37.
    37 GENERAL NOTES During this presentation some very explicit Java code may be shown. No ducks were harmed during the making of this presentation. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 38.
    38 JVM LANGUAGES Jython Java ? JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 39.
    39 JVM LANGUAGES Jython Java Clojure JVM ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 40.
    40 CLOJURE Clojure is Lisp Clojure is a good Lisp Clojure has a more functional flavor than Common Lisp; stateful programming is banned unless in very controlled ways Clojure lives on the JVM and perhaps its rejection of state is a reaction to the heavily stateful model of JVM Clojure is not a pure functional language by any means ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 41.
    41 JVM LANGUAGES Jython Implementation of Python in Java Jython calls Java ~ Clojure New Programming Languages built on the JVM Design choices in Clojure reflect design choices of the JVM Interoperability ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 42.
    42 CLOJURE ~ Good Parts ~ Functional Programming Laziness Full Macros Multi-Methods Immutable types, STM & Concurrency Model ~ Bad Parts ~ “Java” ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 43.
    43 ATOMIC TYPES Integers Floating Point Numbers Ratios (3/4 is not 0.75, is ¾) BigDecimal Strings (“foo”) Booleans (true, false) Nil (nil) Characters (a, b) :keywords regexp’s (#“foo.*”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 44.
    44 SEQUENCE TYPES Python Common Lisp Clojure Type Syntax Type Syntax Type Syntax Random access list [1, 2] vector #(1 2) vector [1 2] sequence Linked List - No list (1 2) list (1 2) Set set {1, 2} No No set #{1 2} Map dict {1:2, 3:4} hash-table No vector {1 2, 3 4} Clojure collections In Clojure all collections are immutable; implement corresponding all the functions return a new collections – as usual, Java collections interfaces immutability allows easy data sharing – vector, list List set Set map Map ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 45.
    45 CLOJURE EXAMPLE (defn rember [a lat]   (cond    (empty? lat) '()    (= (first lat) a) (rest lat)    :else (cons           (first lat)           (rember a (rest lat))))) (rember 4 '(1 2 3 4 5 6 4)) ; => (1 2 3 5 6 4) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 46.
    46 TAIL CALL OPTIMIZATION (defn multirember [a lat]   (letfn       [(multirember-aux [source sink]                    (if (seq source)                      (if (= (first source) a)                        (recur (rest source) sink)                        (recur (rest source)                               (conj sink (first source))))                      sink))]     (multirember-aux lat []))) (take 10 (multirember 4 '(1 2 3 4 5 6 4)) (multirember 4 (iterate inc 0))) ; => [1 2 3 5 6] ; Evaluation aborted. ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 47.
    47 LAZINESS (defn lazy-multirember [a lat]   (letfn       [(multirember-aux [source]                         (lazy-seq                          (if (seq source)                            (if (= (first source) a)                              (multirember-aux (rest source))                              (cons (first source)                                    (multirember-aux (rest source))))                           '())))]     (multirember-aux lat))) (take 10 (lazy-multirember 4 (iterate inc 0))) ; => (0 1 2 3 5 6 7 8 9 10)
  • 48.
    48 NAMESPACES & MODULES (ns example.namespace) (ns example.namespace (:require clojure.set)) Introduces a new namespace. With def (and defn, …) stuff is (ns example.namespace added to namespaces. (:require [clojure.set :as s])) (ns example.namespace (ns example.namespace (:use clojure.string)) (:import [java.util HashMap])) (ns example.namespace (:use [clojure.string :only [capitalize]])) (ns example.namespace (:use [clojure.string :exclude [capitalize]]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 49.
    49 CALLING JAVA Java Clojure Jython import app.model.Person; (import [app.model Person]) from app.model import Person new Person() (new Person) Person() (Person.) person.getFullName() (. getFullName person) person.getFullName() (.getFullName person) Locale.JAPAN (. Locale JAPAN) Locale.JAPAN Locale/JAPAN Integer.valueOf(“42”) (. Integer valueOf "42") java.lang.Integer.valueOf('42') (Integer/valueOf “42”) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 50.
    50 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton] (gui-sample/build-gui            [java.awt.event ActionListener])) "Rock & Roll" (defn build-gui [title message] "Hello, world!”)   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button                         (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message))))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 51.
    51 PROXIES (ns gui-sample   (:import [javax.swing JFrame JButton]            [java.awt.event ActionListener])) (defn build-gui [title message]   (let [frame (JFrame. title)         button (JButton. "CLICK")         px (proxy [ActionListener] []                           (actionPerformed [evt]                                            (println message)))]     (.addActionListener button px)     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true) px))      (update-proxy p {"actionPerformed" (fn [this evt] (println "foo!"))}) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 52.
    52 GEN-CLASS (ns example.ClassExample   (:gen-class    :name example.ClassExample    :extends Object    :implements []    :methods [ [foo [java.util.Collection] int]              ^{:static true} [show [java.util.Collection] void]])   (:import (java.util Collection))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 53.
    53 GEN-CLASS (2) (defn show [coll] (defn -show [coll]   (if (seq coll)   (show coll))     (do       (print (first coll)) (defn -foo [this coll]       (recur (rest coll)))   (let [coll (seq coll)]     (println "")))     (if coll (count coll) -1))) >>> import example >>> example.ClassExample.show([1, 2, 3]) 123 >>> ce = example.ClassExample() >>> ce.foo([1, 2, 3]) 3
  • 54.
    54 IMPLEMENTING PYOBJECTS IN CLOJURE (ns clj.ImmutableList (:gen-class :name clj.ImmutableList :extends org.python.core.PyObject :implements [clojure.lang.IPersistentList] :state state :init init :constructors {[java.util.Collection], []}) (:import [org.python.core PyObject PyInteger Py])) (defn -init [coll] [[coll] (apply list coll)]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 55.
    55 IMPLEMENTING PYOBJECTS IN CLOJURE import clj (ns clj.ImmutableList (:gen-class py_list = ['a', 'b', 'c'] :name clj.ImmutableList my_list = clj.ImmutableList(py_list) :extends org.python.core.PyObject :implements [clojure.lang.IPersistentList] :state state :init init :constructors {[java.util.Collection], []}) (:import [org.python.core PyObject PyInteger Py])) (defn -init [coll] [[coll] (apply list coll)]) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 56.
    56 IMPLEMENTING PYOBJECTS IN CLOJURE (2) (defmacro delegate-to-state [sym] (defn -cons [this other] `(defn ~(symbol (str "-" sym)) (cons (.state this) other)) [this#] (~sym (.state this#)))) (defn -equiv [this other] (= (.state this) other)) (delegate-to-state peek) (delegate-to-state pop) (delegate-to-state count) (delegate-to-state empty) (delegate-to-state seq) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 57.
    57 IMPLEMENTING PYOBJECTS IN CLOJURE (2) (defmacro delegate-to-state [sym] (defn -cons [this other] `(defn ~(symbol (str "-" sym)) (cons (.state this) other)) [this#] (~sym (.state this#)))) (defn -equiv [this other] print(.state this) other)) (= my_list.peek() (delegate-to-state peek) print my_list.pop() (delegate-to-state pop) print my_list.count() (delegate-to-state count) print my_list.empty() (delegate-to-state empty) print my_list.seq() (delegate-to-state seq) print my_list.cons('d') print my_list.equiv(py_list) print my_list.equiv(['a', 'b', 'c']) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 58.
    58 IMPLEMENTING PYOBJECTS print my_list[0] IN CLOJURE (3) print my_list[1] print my_list[2] (defn -__finditem__ [this index] print my_list[2.4] (let [index (if (instance? Number index) index try: (Py/tojava index Number))] print my_list[3] except IndexError, e: (try print e (Py/java2py (nth (.state this) index)) try: (catch IndexOutOfBoundsException e print my_list['a'] (throw (Py/IndexError (.toString e))))))) except TypeError, e: print e try: my_list[0] = 1 except TypeError, e: print e ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 59.
    59 CLOJURE RT from clojure.lang import RT, Compiler source = ''' (ns rember) Compiler.load(java.io.StringReader(source)) (defn rember [a lat] rember = RT.var('rember', 'rember') (cond print rember.invoke(2, range(4)) (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat))))) ''' ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 60.
    60 CLOJURE DECORATOR import pyclj @pyclj.clojure def rember(a, lat):     ’’’(defn rember "Remove first occurrence of a from lat" [a lat] (cond (empty? lat) '() (= (first lat) a) (rest lat) :else (cons (first lat) (rember a (rest lat)))))’’’ if __name__ == '__main__':     print rember(2, range(4))     help(rember) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 61.
    61 IMPLEMENTATION def clojure(fn):     """Decorator that substitutes an empty python function with clojure in the doc with a callable which delegates to the clojure function. """     clj_namespace = determine_clojure_namespace(fn)     clojure_fnc = build_clojure_function_object(clj_namespace, fn)     fn.__doc__ = get_docs(clojure_fnc)     def aux(*args):         return clojure_fnc.invoke(*args)     functools.update_wrapper(aux, fn)     return aux ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 62.
    62 IMPLEMENTATION (2) def determine_clojure_namespace(fn):     try:         clj_namespace = fn.__module__     except AttributeError:         clj_namespace = 'user'     return clj_namespace def get_docs(clojure_fnc):     meta = clojure_fnc.meta()     return meta.get(Keyword.intern('doc')) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 63.
    63 IMPLEMENTATION (3) def build_clojure_function_object(clj_namespace, fn):     clojure_code = '(ns %s)n%s' % (         clj_namespace,         fn.__doc__)     clojure_compile_string(clojure_code)     clojure_fnc = RT.var(clj_namespace, fn.func_name)     return clojure_fnc ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 64.
    64 CALLING JYTHON FROM CLOJURE (defn make-factory [modulename klassname]   (let [interpreter (PythonInterpreter.)          import-command (str-join " " ["from" modulename "import" klassname])]     (.exec interpreter import-command)     (.get interpreter klassname))) (def spam-and-eggs (make-factory "example" "SpamAndEggs")) (def inst (.__call__ spam-and-eggs (Py/java2py 1))) (println inst) (println (.invoke inst "hasSpam"))
  • 65.
    65 CALLING JYTHON FROM CLOJURE (defn make-factory [modulename klassname]   (let [interpreter (PythonInterpreter.) class SpamAndEggs(object):          import-command (str-join " " ["from" modulename     def __init__(self, eggs): "import" klassname])]         self.eggs = eggs     (.exec interpreter import-command)     (.get interpreter klassname))) hasSpam(self):     def         return True (def spam-and-eggs (make-factory "example" "SpamAndEggs"))     def getEggs(self): (def inst (.__call__ spam-and-eggs (Py/java2py 1)))         return self.eggs (println inst)     def __repr__(self): (println (.invoke inst "hasSpam"))         return 'Spam and %s eggs.' % self.eggs
  • 66.
    66 CALLING JYTHON FROM CLOJURE (PT. 2) (defn make-factory   [module klassname]   (let [interpreter (PythonInterpreter.)         import-command (str-join " " ["from" module "import" klassname])]     (.exec interpreter import-command)     (let [klass (.get interpreter klassname)]       (fn [& args]         (.__call__ klass           (into-array PyObject             (map #(Py/java2py %) args))))))) (def spam-and-eggs (make-factory "example" "SpamAndEggs")) (def inst (spam-and-eggs 1))
  • 67.
    67 THROW MACROS IN (defmacro pyclass [q-class jtype]   (let [[klass-name module-name] (split-module-and-class q-class)]     `(def ~(symbol klass-name)       (make-factory ~(str module-name) ~(str klass-name) ~jtype)))) (pyclass example.PrintSomething java.awt.event.ActionListener) (def evt-printer (PrintSomething)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 68.
    68 MAKE-FACTORY (AGAIN) (defn make-factory [module klassname interface] (let [interpreter (PythonInterpreter.) import-command (str-join " " ["from" module "import" klassname])] (.exec interpreter import-command) (let [klass (.get interpreter klassname)] (fn [& args] (.__tojava__ (.__call__ klass (into-array PyObject (map #(Py/java2py %) args))) interface))))) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 69.
    69 BACK TO THE BEGINNING (defn build-gui [title]   (let [frame (JFrame. title)         button (JButton. "CLICK")]     (.addActionListener button (PrintSomething))     (.. frame getContentPane (add button))     (.pack frame)     (.setVisible frame true)     frame)) ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>
  • 70.
    70 CONCLUSION Thanks for Your Kind Attention https://github.com/rik0/PyCLJ_Examples https://github.com/rik0/pyclj ENRICO FRANCHI <EFRANCHI@CE.UNIPR.IT>