Erlang 杂记 IV
休假回来,调整一下状态,先把Evernote里面一些比较零散的东西整理出来;过去一个月对于Erlang开发者还是有些惊喜的,比如《 Erlang / OTP 并发编程实战》终于出版了;比如<Building.Web.Applications.with.Erlang>也可以看到英文版了.下面第一条消息就是关于Erlang的另外一本好书:《Learn You Some Erlang》
Learn You Some Erlang 两则
Erlang学习有一个非常棒的网站: http://learnyousomeerlang测试数据/
现在有两则关于它的消息:
[1] 首先是这本书的Kindle版本, 能够在移动设备上阅读这本书,真的是非常方便;其实不仅仅是Kindle 其它支持mobi格式的都可以完美显示;甚至你可以使用源文件自己编译成为其它格式,比如epub;
github地址: https://github测试数据/igstan/learn-you-some-erlang-kindle
[2] 这个网站的出版物已经发行,其中文版由 @淘宝褚霸 翻译,可以预见到这又将成为中文资料的经典之作
http://book.douban测试数据/subject/10822017/
string To Erlang Term 一个更为考虑更为完善的方法
下面是可以解决的:
1 > E=fun(S) ->{ok,Scanned,_} = erl_scan: string(S),
{ok,Parsed} = erl_parse: parse_exprs(Scanned),
erl_eval: exprs(Parsed,[]) end.
#Fun<erl_eval. 6 . 111823515 >
2 > E( " {quit,tom}\n " ++ " . " ).
{value,{quit,tom},[]}
3 >
如果是Pid的情况下会存在异常
** exception error: no match of right hand side value
{error,{ 1 ,erl_parse,[ " syntax error before: " , " '<' " ]}}
然后我在这里发现了一个更为完善的做法
https://github测试数据/erlang/otp/blob/master/lib/tv/src/tv_db_search.erl
string_to_term( Str ) ->
case catch erl_scan: string( Str ++ " . " ) of
{ok, ScannedStr, _No} ->
case erl_parse: parse_term(ScannedStr) of
{ok, Term} ->
{ok, Term} ;
_Other ->
%% May be a PID, have to check this, since erl_scan
%% currently cannot handle this case... :-(
case catch list_to_pid( Str ) of
Pid when is_pid(Pid) ->
{ok, Pid} ;
_Error ->
case get(error_msg_mode) of
normal ->
{error, {not_a_term, " Please enter a valid term! " }} ;
haiku ->
{error, {not_a_term, [ " Aborted effort. " ,
" Reflect, repent and retype: " ,
" Enter valid term. " ]}}
end
end
end ;
_Error ->
case get(error_msg_mode) of
normal ->
{error, {not_a_term, " Please enter a valid term! " }} ;
haiku ->
{error, {not_a_term, [ " Aborted effort. " ,
" Reflect, repent and retype: " ,
" Enter valid term. " ]}}
end
end.
binary 替换一例 注意转义符的使用
这个没有什么特别的,只是要注意转义字符的使用
85 > binary: replace(<< " c:\\windows\\abc\\c.txt " >>,<< 92 >>,<< " // " >>,[global]). << " c://windows//abc//c.txt " >> 86 > binary: replace(<< " c:\\windows\\abc\\c.txt " >>,<< " \\ " >>,<< " // " >>,[global]). << " c://windows//abc//c.txt " >> 87 >
ETS表中,根据表名获取ets表id,可用但是繁琐一点
12 > Fun3=fun(Name)->[ ID|| ID <- ets: all(),Name== ets: info(ID,name)] end. #Fun<erl_eval. 6 . 111823515 > 13 > Fun3(inet_db). [inet_db] 14 > Fun3(code). " \r " 15 > Fun3(code_names). [ 4110 ] 16 >
erlang模块下面有一个非常好用的解包方法
下面的解析可以使用string或binary模块自行解析,其实使用erlang:packet直接可以得到结果
Eshell V5. 9 . 1 (abort with ^G)
1 > erlang: decode_packet(http,<< " GET http://HdhCmsTestgoogle测试数据 HTTP/1.1\n " >>,[]).
{ok,{http_request, ' GET ' ,
{absoluteURI,http, " HdhCmsTestgoogle测试数据 " ,undefined, " / " },
{ 1 , 1 }},
<<>>}
2 > erlang: decode_packet( 1 ,<< 3 , " abcd " >>,[]).
{ok,<< " abc " >>,<< " d " >>}
3 > erlang: decode_packet( 1 ,<< 5 , " abcd " >>,[]).
{more, 6 }
4 >
erlang:decode_packet的官方文档地址: http://HdhCmsTesterlang.org/doc/man/erlang.html
Erlang字符串处理的两个开源项目
[1] http://code.google测试数据/p/starling/
Unicode strings for Erlang
Starling is a Unicode string library for Erlang based on ICU , the best implementation of Unicode.
It's implemented as a C pipe driver packaged as an OTP application. Strings are stored as binaries internally. Compatibility layer with the standard string module is provided.
A mailing list has been set up at http://groups.google测试数据/group/starling-discuss .
The project homepage is at http://12monkeys.co.uk/starling .
[2] https://github测试数据/beerriot/icu4e icu4e: Erlang NIF wrappers around icu4c
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分类: Erlang
作者： Leo_wl
出处： http://HdhCmsTestcnblogs测试数据/Leo_wl/
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