[Erlang 0121] 当我们谈论Erlang Maps时,我们谈论什么 Part 3

Erlang/OTP 17.0 has been released 

http://www.erlang.org/download/otp_src_17.0.readme

 

  Erlang/OTP 17.0发布了,不过Maps相关的设计还没有尘埃落定,目前:

             With Maps you may for instance:

              -- M0 = #{ a => 1, b => 2}, % create associations

              -- M1 = M0#{ a := 10 }, % update values

              -- M2 = M1#{ "hi" => "hello"}, % add new associations

              -- #{ "hi" := V1, a := V2, b := V3} = M2. % match keys with
              values

              For information on how to use Maps please see the Reference
              Manual.

              The current implementation is without the following features:

              -- No variable keys

              -- No single value access

              -- No map comprehensions

              Note that Maps is experimental during OTP 17.0.

 

 

另外有一个不兼容的情况: OTP-11782  == erts ==

 The external format for Maps has changed in a way that is not  compatible with the format used in OTP 17.0-rc1 and OTP  17.0-rc2.

 

在这里查看详情:

 

Change the subtag used for maps from 0xB to 0xF

https://github.com/erlang/otp/pull/315

 

Maps 模块对应的文档位置

http://erlang.org/doc/man/maps.html

 

占坑,后续变动将在此更新.

 

Learn You Some Erlang 对Maps内容的增补章节 

http://learnyousomeerlang.com/maps

 

 顺便补几张图:

 

上面的图看不懂?可以参考下面这篇论文,其中简要介绍了Erlang的Tag-Scheme,或者可以去看下本文的第一篇 http://www.cnblogs.com/me-sa/p/when_we_talk_about_erlang_maps_1.html

 

On Preserving Term Sharing in the Erlang Virtual Machine

地址: http://user.it.uu.se/~kostis/Papers/erlang12_sharing.pdf 

摘要:In this paper we describe our experiences and argue through examples why flattening terms during copying is not a good idea for

a language like Erlang. More importantly, we propose a sharing preserving copying mechanism for Erlang/OTP and describe a pub-
licly available complete implementation of this mechanism.