diff options
-rw-r--r-- | ChangeLog | 4 | ||||
-rw-r--r-- | hash.c | 16 |
2 files changed, 20 insertions, 0 deletions
@@ -1,3 +1,7 @@ +Sat Feb 13 21:44:58 2016 Tanaka Akira <akr@fsij.org> + + * hash.c (rb_hash_invert): [DOC] more examples. + Sat Feb 13 17:30:49 2016 Nobuyoshi Nakada <nobu@ruby-lang.org> * lib/uri/generic.rb (URI::Generic#find_proxy): support CIDR in @@ -2217,6 +2217,22 @@ rb_hash_invert_i(VALUE key, VALUE value, VALUE hash) * h = { "n" => 100, "m" => 100, "y" => 300, "d" => 200, "a" => 0 } * h.invert #=> {0=>"a", 100=>"m", 200=>"d", 300=>"y"} * + * If there is no key with the same value, Hash#invert is involutive. + * + * h = { a: 1, b: 3, c: 4 } + * h.invert.invert == h #=> true + * + * The condition, no key with the same value, can be tested by comparing + * the size of inverted hash. + * + * # no key with the same value + * h = { a: 1, b: 3, c: 4 } + * h.size == h.invert.size #=> true + * + * # two (or more) keys has the same value + * h = { a: 1, b: 3, c: 1 } + * h.size == h.invert.size #=> false + * */ static VALUE |