Changes for page ROS Crash Course

Last modified by Leon Poon on 2021/08/30 23:24
From version 2.1
edited by Leon Poon
on 2021/08/23 10:50
Change comment: There is no comment for this version
To version 6.1
edited by Leon Poon
on 2021/08/30 23:24
Change comment: There is no comment for this version

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1 -= C++ Crash Crash Course =
1 +(% class="wikigeneratedid" id="HC2B2BCrashCrashCourse" %)
2 +Using C++.
2 2  
3 3  == Day 1 ==
4 4  
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6 6  
7 7  g++ source1.cpp -o program1
8 8  
9 -Paths, . and .. in navigating directories
10 +Paths, "/" and "." and ".." in navigating directories - absolute vs relative
10 10  
11 -data type - memory, binary
12 +data type - binary itself is meaningless unless you say what information that the binary bits represent
12 12  
13 13  declare variables (int, char, string as series of chars)
14 14  
15 15  statements end with semicolon
16 16  
17 -cstdio library include
18 +cstdio library #include
18 18  
19 19  calling a function - printf
20 20  
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32 32  
33 33  While loop = for loop with empty initialiser/advancement statements
34 34  
35 -Switch - match expression's result to case label
36 +Switch - match expression's result to case label, execute statements until break.
36 36  
37 -Switch vs if-else differences.
38 +Switch vs if-else differences - number of times expressions are evaluated
38 38  
39 -your own function
40 +write your own function
40 40  
41 41  calling with parameters copied as separate set of var values in function
42 42  
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52 52  
53 53  Value overflow because not enough number of bits to represent large numbers.
54 54  
56 +Various integer data types - specifier in printf
57 +
55 55  Homework: implement factorial (1 to 20) calculator
56 56  
60 +in Linux, most things are case-sensitive. (A not equals a)
61 +
57 57  == Day 3 ==
58 58  
59 59  factorial printer - 2 approaches:
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63 63  
64 64  set initial values of vars when declaring otherwise initial values are unpredictable
65 65  
71 +factorial function - implemented in recursive way, closer to mathematical definition
66 66  
73 +stack memory
67 67  
75 +stack frame to store var values in each function call
68 68  
77 +stack overflow/crash (segfault)
78 +
79 +base condition to stop the recursion
80 +
81 +recursive algorithms are common - e.g. when dealing with trees
82 +
83 +spaces in file/directory names and how to navigate - space is special in terminal
84 +
85 +understand names chosen by yourself vs names chosen by other people for your use
86 +
87 +creating ros package - arguments: package name, dependencies
88 +
89 +CMakeLists.txt (.txt file can also be used with other programs)
90 +
91 +cmake = build tool - compile many files in some defined ways
92 +
93 +package.xml - information for ROS
94 +
95 +compiling - carefully read and understand and seek answers to error messages
96 +
97 +msg files - fields declaration with data type
98 +
99 +create cpp file for a node
100 +
101 +quick reading of code for publisher node
102 +
103 +homework: implement message subscriber node according to ROS book
104 +
105 +== Day 4 ==
106 +
107 +message subscriber.
108 +
109 +argc and agrv
110 +
111 +node name during ros::init
112 +
113 +topic advertise/subscribe explained.
114 +
115 +subscribe() only memorises that this node wants messages and what to do with them.
116 +
117 +subscribe() - providing name of function. not calling.
118 +
119 +publisher while ros::ok() loop.
120 +
121 +subscriber spin() loop - handle events.
122 +
123 +the double-colon operator: (1) namespace (2) static member of class
124 +
125 +pointers are memory addresses
126 +
127 +arrow -> operator
128 +
129 +array are elements in sequence in memory.
130 +
131 +char ~*~* = pointer of pointer of char data.
132 +
133 +
69 69