This Week I Learned - 2017 Week 01

Last week post or the whole series.

First week of the new year 2017. A busy and slow week. Busy because wrapping up most of the pending to-do list. Slow due to the progress of clearing up the list. When you're overwhelmed by numerous tasks at hand, the best way is still sleep over it. You can't do much with a tired mind, especially at my age now. You can accomplish lots of thing with a good sleep and fresh mind in the wee hours in the morning, roughly around 4:30 a.m.


Did something happened in July? Darker green means more steps and lighter green, the opposite. To the best of my recollection, I've misplaced my pedometer and resolved to use Google's Fit step counter, which is not entirely accurate. Typically offset by half against my pedometer.

#1 Remember about last week post on adding extra options so we compile the sample D source code? The extra options can be added to the `dmd.conf` configuration file. Following these steps to add them to `dmd.conf` file so that you won't need to type them again and again.

Copy the config file to your home directory
$ cp /etc/dmd.conf $HOME

Append the options, `-fPIC -defaultlib=libphobos2.so` to `DFLAGS` variable.
[Environment32]
DFLAGS=-I/usr/include/dmd/phobos -I/usr/include/dmd/druntime/import
-L-L/usr/lib/i386-linux-gnu -L--export-dynamic -fPIC -defaultlib=libphobos2.so

[Environment64]
DFLAGS=-I/usr/include/dmd/phobos -I/usr/include/dmd/druntime/import-L-L/usr/lib/x86_64-linux-gnu
-L--export-dynamic -fPIC -defaultlib=libphobos2.so

#2 Some new concepts in Modern C++. What is this Resource acquisition is initialization (RAII) I kept reading about? It's a programming idiom is about safe resource management and in C++, through an object's lifetime. Resources are initialized and acquired in object's constructor and released through object's destructor. In other words, resources are cleaned up when the scope of code have exit. See the diagram below for further understanding. Other programming languages implemented this idiom through a try/finally block instead through an object's destructor.


Second, is the concept of template. As C++ is a statically typed programming language (type checking is done at compile-time rather than run-time, see this good example), when you declare or initialize any variables, you need to specific a data type. What if you need to pass in a variable to a function which can accept different kinds of numeric data, an integer or and a floating-point number? This is when you will use template to specific a generic type.

Example of the function templates is shown below. You can pass in different kind of data types like integer, floating-number, or character.
#include <iostream>
using namespace std ;
//max returns the maximum of the two elements
template 
T max(T a, T b) {
    return a > b ? a : b ;
}

While we're at Modern C++, there is a list of resources which can get you started as well as the C++11/14/17 feature list. For learning C++ today, the minimum standard you should follow is C++11.

#3 Instead of listening to music while coding, why not listen to development related podcasts like Software Engineering Radio, The Changelog, The Bike Shed, or FLOSS weekly? All this better than some annoying pig squeal and snort noises.

#4 Accidentally messed up my commit dates while testing Git. Need to updates some old commits. However, you have to force push to override the history.
$ git filter-branch --env-filter \
'if [ $GIT_COMMIT = f1d2d2f924e986ac86fdf7b36c94bcdf32beec15 ]
then
    export GIT_AUTHOR_DATE="Sun Jan 7 01:02:03 2017 +0800"
    export GIT_COMMITTER_DATE="Sun Jan 7 01:02:03 2017 +0800"
fi'

$ git push -f origin master

And to remove all the uncommitted files from your project, you can use this Git command. However, be careful as it also remove my Vim's swap files (.swp). Did I forget to set a global path for all Vim's swap files?
$ git clean -d -f -x

#5 As I'm starting to build something in C++, creating and maintaining a Makefile is quite a hassle. Luckily we have CMake which helps let us bootstrap the Makefile fast. One thing I've learned when using CMake is compile and build your program in a specific folder. This will prevent all the temporary files generated by CMake from cluttering your root folder.
$ mkdir build && cd build
$ cmake ../
$ tree -L 1 .
.
├── CMakeCache.txt
├── CMakeFiles
├── cmake_install.cmake
└── Makefile


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