http://www.ipb.uni-bonn.de/wp-content/uploads/2018/05/lecture_2.pdf
make bash file executable
Wall: Warning all
Wextra: add even more extra Warning
Werror: treat Warnings as errors
by default, there's no optimization.
-O0
-O3 -Ofaster
"segmentation fault" means you are using some unallowed memory.
use reference to avoid copy, and save a lot time!
explaining how reference as function variable works.
Announce default variables only in declaration (typo above...).
sort, sumation, multiplication standard operation in std::vector
every header file should include "#pragma once", otherwise you would get wierd errors.
the compiler doesn't know the definition of the test.cpp.
simply add the 2nd line will make the "c++ main.cpp ... " work, but no output!
build the test.cpp first, and include the result .o file into main.cpp building.
c++ workflow!!!
.o file is binary and only machine can read it.
maybe there's a branch of changing now in makefile. but this file is simple and readable.
