Changes for page ROS Crash Course

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...	...	@@ -1,5 +1,4 @@
1		-(% class="wikigeneratedid" id="HC2B2BCrashCrashCourse" %)
2		-Using C++.
	1	+= C++ Crash Crash Course =
3	3
4	4	== Day 1 ==
5	5
...	...	@@ -7,15 +7,15 @@
7	7
8	8	g++ source1.cpp -o program1
9	9
10		-Paths, "/" and "." and ".." in navigating directories - absolute vs relative
	9	+Paths, . and .. in navigating directories
11	11
12		-data type - binary itself is meaningless unless you say what information that the binary bits represent
	11	+data type - memory, binary
13	13
14	14	declare variables (int, char, string as series of chars)
15	15
16	16	statements end with semicolon
17	17
18		-cstdio library #include
	17	+cstdio library include
19	19
20	20	calling a function - printf
21	21
...	...	@@ -33,11 +33,11 @@
33	33
34	34	While loop = for loop with empty initialiser/advancement statements
35	35
36		-Switch - match expression's result to case label, execute statements until break.
	35	+Switch - match expression's result to case label
37	37
38		-Switch vs if-else differences - number of times expressions are evaluated
	37	+Switch vs if-else differences.
39	39
40		-write your own function
	39	+your own function
41	41
42	42	calling with parameters copied as separate set of var values in function
43	43
...	...	@@ -53,82 +53,18 @@
53	53
54	54	Value overflow because not enough number of bits to represent large numbers.
55	55
56		-Various integer data types - specifier in printf
57		-
58	58	Homework: implement factorial (1 to 20) calculator
59	59
60		-in Linux, most things are case-sensitive. (A not equals a)
61		-
62	62	== Day 3 ==
63	63
64	64	factorial printer - 2 approaches:
65	65
66		-1. for-loop that goes 1 to 20 and each loop calls fact(n ) function and prints return.
	61	+1. for-loop that goes 1 to 20 and each loop calls fact(n) function and prints return.
67	67	1. for-loop that goes 1 to 20 and multiplies once each time and print.
68	68
69	69	set initial values of vars when declaring otherwise initial values are unpredictable
70	70
71		-factorial function - implemented in recursive way, closer to mathematical definition
72	72
73		-stack memory
74	74
75		-stack frame to store var values in each function call
76	76
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		-
134	134