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Java example source code file (evaluation.clj)

This example Java source code file (evaluation.clj) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

boolean, collections, compiler, compilerexception, created, eval, java, literals, metadata, second, string

The evaluation.clj Java example source code

;   Copyright (c) Rich Hickey. All rights reserved.
;   The use and distribution terms for this software are covered by the
;   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;   which can be found in the file epl-v10.html at the root of this distribution.
;   By using this software in any fashion, you are agreeing to be bound by
;   the terms of this license.
;   You must not remove this notice, or any other, from this software.


;;  Tests for the Clojure functions documented at the URL:
;;
;;    http://clojure.org/Evaluation
;;
;;  by J. McConnell
;;  Created 22 October 2008

(ns clojure.test-clojure.evaluation
  (:use clojure.test))

(import '(java.lang Boolean)
        '(clojure.lang Compiler Compiler$CompilerException))

(defmacro test-that
  "Provides a useful way for specifying the purpose of tests. If the first-level
  forms are lists that make a call to a clojure.test function, it supplies the
  purpose as the msg argument to those functions. Otherwise, the purpose just
  acts like a comment and the forms are run unchanged."
  [purpose & test-forms]
  (let [tests (map
                #(if (= (:ns (meta (resolve (first %))))
                        (the-ns 'clojure.test))
                   (concat % (list purpose))
                   %)
                test-forms)]
    `(do ~@tests)))

(deftest Eval
  (is (= (eval '(+ 1 2 3)) (Compiler/eval '(+ 1 2 3))))
  (is (= (eval '(list 1 2 3)) '(1 2 3)))
  (is (= (eval '(list + 1 2 3)) (list clojure.core/+ 1 2 3)))
  (test-that "Non-closure fns are supported as code"
             (is (= (eval (eval '(list + 1 2 3))) 6)))
  (is (= (eval (list '+ 1 2 3)) 6)))

; not using Clojure's RT/classForName since a bug in it could hide a bug in
; eval's resolution
(defn class-for-name [name]
  (java.lang.Class/forName name))

(defmacro in-test-ns [& body]
  `(binding [*ns* *ns*]
     (in-ns 'clojure.test-clojure.evaluation)
     ~@body))

;;; Literals tests ;;;

(defmacro #^{:private true} evaluates-to-itself? [expr]
  `(let [v# ~expr
         q# (quote ~expr)]
     (is (= (eval q#) q#) (str q# " does not evaluate to itself"))))

(deftest Literals
  ; Strings, numbers, characters, nil and keywords should evaluate to themselves
  (evaluates-to-itself? "test")
  (evaluates-to-itself? "test
                        multi-line
                        string")
  (evaluates-to-itself? 1)
  (evaluates-to-itself? 1.0)
  (evaluates-to-itself? 1.123456789)
  (evaluates-to-itself? 1/2)
  (evaluates-to-itself? 1M)
  (evaluates-to-itself? 999999999999999999)
  (evaluates-to-itself? \a)
  (evaluates-to-itself? \newline)
  (evaluates-to-itself? nil)
  (evaluates-to-itself? :test)
  ; Boolean literals should evaluate to Boolean.{TRUE|FALSE}
  (is (identical? (eval true) Boolean/TRUE))
  (is (identical? (eval false) Boolean/FALSE)))

;;; Symbol resolution tests ;;;

(def foo "abc")
(in-ns 'resolution-test)
(def bar 123)
(def #^{:private true} baz 456)
(in-ns 'clojure.test-clojure.evaluation)

(defn a-match? [re s] (not (nil? (re-matches re s))))

(defmacro throws-with-msg
  ([re form] `(throws-with-msg ~re ~form Exception))
  ([re form x] `(throws-with-msg
                  ~re
                  ~form
                  ~(if (instance? Exception x) x Exception)
                  ~(if (instance? String x) x nil)))
  ([re form class msg]
       `(let [ex# (try
                    ~form
                    (catch ~class e# e#)
                    (catch Exception e#
                      (let [cause# (.getCause e#)]
                        (if (= ~class (class cause#)) cause# (throw e#)))))]
          (is (a-match? ~re (.toString ex#))
              (or ~msg
                  (str "Expected exception that matched " (pr-str ~re)
                       ", but got exception with message: \"" ex#))))))

(deftest SymbolResolution
  (test-that
    "If a symbol is namespace-qualified, the evaluated value is the value
     of the binding of the global var named by the symbol"
    (is (= (eval 'resolution-test/bar) 123)))

  (test-that
    "It is an error if there is no global var named by the symbol"
    (throws-with-msg
      #".*Unable to resolve symbol: bar.*" (eval 'bar)))

  (test-that
    "It is an error if the symbol reference is to a non-public var in a
    different namespace"
    (throws-with-msg
      #".*resolution-test/baz is not public.*"
      (eval 'resolution-test/baz)
      Compiler$CompilerException))

  (test-that
    "If a symbol is package-qualified, its value is the Java class named by the
    symbol"
    (is (= (eval 'java.lang.Math) (class-for-name "java.lang.Math"))))

  (test-that
    "If a symbol is package-qualified, it is an error if there is no Class named
    by the symbol"
    (is (thrown? Compiler$CompilerException (eval 'java.lang.FooBar))))

  (test-that
    "If a symbol is not qualified, the following applies, in this order:

      1. If it names a special form it is considered a special form, and must
         be utilized accordingly.

      2. A lookup is done in the current namespace to see if there is a mapping
         from the symbol to a class. If so, the symbol is considered to name a
         Java class object.

      3. If in a local scope (i.e. in a function definition), a lookup is done
         to see if it names a local binding (e.g. a function argument or
         let-bound name). If so, the value is the value of the local binding.

      4. A lookup is done in the current namespace to see if there is a mapping
         from the symbol to a var. If so, the value is the value of the binding
         of the var referred-to by the symbol.

      5. It is an error."

    ; First
    (doall (for [form '(def if do let quote var fn loop recur throw try
                         monitor-enter monitor-exit)]
             (is (thrown? Compiler$CompilerException (eval form)))))
    (let [if "foo"]
      (is (thrown? Compiler$CompilerException (eval 'if)))

    ; Second
      (is (= (eval 'Boolean) (class-for-name "java.lang.Boolean"))))
    (let [Boolean "foo"]
      (is (= (eval 'Boolean) (class-for-name "java.lang.Boolean"))))

    ; Third
    (is (= (eval '(let [foo "bar"] foo)) "bar"))

    ; Fourth
    (in-test-ns (is (= (eval 'foo) "abc")))
    (is (thrown? Compiler$CompilerException (eval 'bar))) ; not in this namespace

    ; Fifth
    (is (thrown? Compiler$CompilerException (eval 'foobar)))))

;;; Metadata tests ;;;

(defstruct struct-with-symbols (with-meta 'k {:a "A"}))

(deftest Metadata

  (test-that
    "find returns key symbols and their metadata"
    (let [s (struct struct-with-symbols 1)]
      (is (= {:a "A"} (meta (first (find s 'k))))))))

;;; Collections tests ;;;
(def x 1)
(def y 2)

(deftest Collections
  (in-test-ns
    (test-that
      "Vectors and Maps yield vectors and (hash) maps whose contents are the
      evaluated values of the objects they contain."
      (is (= (eval '[x y 3]) [1 2 3]))
      (is (= (eval '{:x x :y y :z 3}) {:x 1 :y 2 :z 3}))
      (is (instance? clojure.lang.IPersistentMap (eval '{:x x :y y})))))

  (in-test-ns
    (test-that
      "Metadata maps yield maps whose contents are the evaluated values of
      the objects they contain. If a vector or map has metadata, the evaluated
      metadata map will become the metadata of the resulting value."
      (is (= (eval #^{:x x} '[x y]) #^{:x 1} [1 2]))))

  (test-that
    "An empty list () evaluates to an empty list."
    (is (= (eval '()) ()))
    (is (empty? (eval ())))
    (is (= (eval (list)) ())))

  ;aargh, fragile tests, please fix
  #_(test-that
    "Non-empty lists are considered calls"
    (is (thrown? Compiler$CompilerException (eval '(1 2 3))))))

(deftest Macros)

(deftest Loading)

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