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comparison graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/runtime/SLNull.java @ 21689:ed234a3178af

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Behavior of null-like values is now part of the TCK
author Jaroslav Tulach <jaroslav.tulach@oracle.com>
date Wed, 03 Jun 2015 10:17:19 +0200
parents 1d3c23e675ed
children c76742cc2c6f
comparison
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21688:889b45a0dedd 21689:ed234a3178af
20 * or visit www.oracle.com if you need additional information or have any 20 * or visit www.oracle.com if you need additional information or have any
21 * questions. 21 * questions.
22 */ 22 */
23 package com.oracle.truffle.sl.runtime; 23 package com.oracle.truffle.sl.runtime;
24 24
25 import com.oracle.truffle.api.interop.ForeignAccessFactory;
26 import com.oracle.truffle.api.interop.TruffleObject;
27
25 /** 28 /**
26 * The SL type for a {@code null} (i.e., undefined) value. In Truffle, it is generally discouraged 29 * The SL type for a {@code null} (i.e., undefined) value. In Truffle, it is generally discouraged
27 * to use the Java {@code null} value to represent the guest language {@code null} value. It is not 30 * to use the Java {@code null} value to represent the guest language {@code null} value. It is not
28 * possible to specialize on Java {@code null} (since you cannot ask it for the Java class), and 31 * possible to specialize on Java {@code null} (since you cannot ask it for the Java class), and
29 * there is always the danger of a spurious {@link NullPointerException}. Representing the guest 32 * there is always the danger of a spurious {@link NullPointerException}. Representing the guest
30 * language {@code null} as a singleton, as in {@link #SINGLETON this class}, is the recommended 33 * language {@code null} as a singleton, as in {@link #SINGLETON this class}, is the recommended
31 * practice. 34 * practice.
32 */ 35 */
33 public final class SLNull { 36 public final class SLNull implements TruffleObject {
34 37
35 /** 38 /**
36 * The canonical value to represent {@code null} in SL. 39 * The canonical value to represent {@code null} in SL.
37 */ 40 */
38 public static final SLNull SINGLETON = new SLNull(); 41 public static final SLNull SINGLETON = new SLNull();
50 */ 53 */
51 @Override 54 @Override
52 public String toString() { 55 public String toString() {
53 return "null"; 56 return "null";
54 } 57 }
58
59 @Override
60 public ForeignAccessFactory getForeignAccessFactory() {
61 return SLFunctionForeignAccess.INSTANCE;
62 }
55 } 63 }