Regular expression describes a pattern of matching string Can be used to detect/replace/take out specific substring
Syntax
symbol
description
example
^
match the beginning of he line
[ABC]
match all char in […]
[aeiou]: google runoob taobao
[^ABC]
match all except those in […]
[A-Z]
describe an interval
[a-z] matchs all lower case char
(…)
set groups
\1…\n
match the same elements as nth group
{n}
the front element repeats n times
{n,}
the front element repeats at least n times
{n,m}
the front element repeats at least n and at most m times
.
match any char except (\n,\r), same with [^\n\r]
\s\S
match all, \s:match all space char, \S:match all non space char, ‘return’ not included
\w
match letter,number,underline, equal to [A-Za-z0-9 ]
\cx
match the control char indicated by x(A-Z/a-z)
\cM: Control-M or return char
\f
match a page change char
\n\r
match a return symbol
\t
match a tab
\v
match a vertical tab
$
match the end of the string, to match $ itself, use $
*
match the front subexpression multiple or zero times, use \* to match *
+
match the front subexpression multiple or one times, use \+
.
match any single char except \n
[
mark the beginning of a []expression
?
match the front subexpression one or zero times, or indicate a non-greedy qualifier
|
logic or
Application in Cpp
In cpp, we use std::regex to express regular expression, supporting ECMAScripts as default.
Match
Use regex_match() to match xml (or html) format:
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std::regex reg("<.*>.*</.*>");
bool ret = std::regex_match("<xml>value</xml>",reg); assert(ret);
bool ret = std::regex_match("<html>value</html>",reg); assert(ret);
bool ret = std::regex_match("<xml>value<xml>",reg); assert(ret);
Search
Use std::regex_search. As long as there exists targets in the string, it will return.
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std::regex reg("<(.*)>(.*)</(\\1)>"); std::cmatch m; auto ret = std::regex_search("123<xml>value</xml>456", m, reg); if (ret){ for (auto& elem : m) std::cout<<elem<<std::endl; }
Study note for ROS * Core Concept ** Node and ROS Master *** Node implement functions for purposes support various language can have thousands of nodes *** ROS Master mange the registion and name of various nodes support(trace and record) communication between different nodes for nodes to find each other provide parameter server(store global variables...)[[about parameter]] ** Communication between nodes | | Topic | Service | |--------------------+---------------------+----------------| | sync | n | y | | model | publish/subscribe | service/client | | protocol | ROSTCP/ROSUDP | ROSTCP/ROSUDP | | response | n | y | | buffer | y | n | | real-time | weak | strong | | nodes relationship | multi/one to multi | one to multi | | scene | data transformation | logic process | *** Topic Node(publisher)->Topic(/example)&Message_Tyoe(std_msgs/String)->other ROS nodes(subscriber) Message: define the data type and struct of data, defined by .msg file async *** Service C/S model(Client/Server) client send requests, server return response data defined by .srv file, defines the structure of the requests and response ROS node(Service Server) ^ |response request| v ROS node(Service Client) sync ** Parameter <<about parameter>> talker -> ROS master : setParam("foo",1) listener -> ROS master: getParam("foo") ROS master ->listener: {"foo",1}
multiple variable dictionary for storing static nonbinary configuration, not suitable for dynamic ** File system *** package Basic unit in ROS, include the src of nodes, cfg, data def *** package manifest record the basic information of packages *** Meta packages orgnize multi packages for one common purpose * Commond Line Tools ** rqt_graph visualize tool display the calculate process graph ** rosnode display node information *** rosnode list list all node default node /rosout *** rosnode info /turtle_sim show info of a node ** rostopic usage like rosnode(list,info) *** rostopic pub /../.. data_structure data publish message as a topic add -r num to repeat sending at rate num/s ** rosmsg *** rosmsg show data_structure show the data structure ** rosservice | commond addition | | |------------------------+-----------------------------------| | list | list all service the node provide | | call service_name data | | ** rosbag | command addition | | | | |-------------------------+-----------------------------------------------+--------+-----------------| | record -a -O cmd_record | record the topic data in the system | -a:all | -O as a package | | play cmd_record.bag | play the recorded data of previous simulation | | | | | | | | * setup workspace and function package ** workspace *** overview | src | source space | | | build | build space | no need to touch | | devel | develop space | script, executable file | | install | install sapce | |
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