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-rw-r--r--hash.c34
1 files changed, 33 insertions, 1 deletions
diff --git a/hash.c b/hash.c
index 0d4d433..e2f7345 100644
--- a/hash.c
+++ b/hash.c
@@ -2414,7 +2414,39 @@ env_update(env, hash)
* Hashes have a <em>default value</em> that is returned when accessing
* keys that do not exist in the hash. By default, that value is
* <code>nil</code>.
- *
+ *
+ * <code>Hash</code> uses <code>key.eql?</code> to test keys for equality.
+ * If you need to use instances of your own classes as keys in a <code>Hash</code>,
+ * it is recommended that you define both the <code>eql?</code> and <code>hash</code>
+ * methods. The <code>hash</code> method must have the property that
+ * <code>a.eql?(b)</code> implies <code>a.hash == b.hash</code>.
+ *
+ * class MyClass
+ * attr_reader :str
+ * def initialize(str)
+ * @str = str
+ * end
+ * def eql?(o)
+ * o.is_a?(MyClass) && str == o.str
+ * end
+ * def hash
+ * @str.hash
+ * end
+ * end
+ *
+ * a = MyClass.new("some string")
+ * b = MyClass.new("some string")
+ * a.eql? b #=> true
+ *
+ * h = {}
+ *
+ * h[a] = 1
+ * h[a] #=> 1
+ * h[b] #=> 1
+ *
+ * h[b] = 2
+ * h[a] #=> 2
+ * h[b] #=> 2
*/
void