Programming on Raveen Kumar

Contacts Organizer cli app

Fri, 04 Sep 2026 00:00:00 +0000

TODO:

Power of 2s

Thu, 20 Apr 2023 00:00:00 +0000

n	2^n
0	1
1	2
2	4
3	8
4	16
5	32
6	64
7	128
8	256
9	512
10	1,024
11	2,048
12	4,096
13	8,192
14	16,384
15	32,768
16	65,536
17	131,072
18	262,144
19	524,288
20	1,048,576

Reading notes - Designing a Video Game hardware in Verilog

Thu, 20 Apr 2023 00:00:00 +0000

Book: Designing Video Game Hardware in Verilog, Steven Hugg (2018).

2023-04-20-power-of-2s

Byte - 8 bits Nibble - 4 bits

/*
A clock divider in Verilog, using the cascading
flip-flop method.
*/

module clock_divider(
  input clk,
  input reset,
  output reg clk_div2,
  output reg clk_div4,
  output reg clk_div8,
  output reg clk_div16
);

  // simple ripple clock divider
  
  always @(posedge clk)
    clk_div2 <= reset ? 0 : ~clk_div2;

  always @(posedge clk_div2)
    clk_div4 <= ~clk_div4;

  always @(posedge clk_div4)
    clk_div8 <= ~clk_div8;

  always @(posedge clk_div8)
    clk_div16 <= ~clk_div16;

endmodule

Static timing anaysis

Setup time and hold time are timing constraints that must be met in digital circuits to ensure correct data transfer between logic elements. These constraints are important to consider in the design of synchronous digital circuits, which use a clock signal to synchronize the transfer of data between flip-flops or other storage elements.

Emacs symbol search at point

Wed, 12 Apr 2023 00:00:00 +0000

To enter symbol search press M-s . this with execute isearch-forward-symbol-at-point function. This is similar to vim’s * key. I accitentally pressed it instead of M-s h . and found it while trying to highlight a symbol, lol.

Mark ring and Jumplist with emacs and helm

Fri, 07 Apr 2023 00:00:00 +0000

Like vim, emacs has an alternative to jump list. It is called mark rings but its difficult to use. Fortunately there is a helm and counsel function to help us navigate the mark rings. Add this following command to emacs init file,

(global-set-key (kbd "C-c '") 'helm-all-mark-rings)

I use C-c ' to browse mark rings.

Stop asking tags table to be reset every time a new file is visited in a different project

Fri, 07 Apr 2023 00:00:00 +0000

(setq tags-add-tables nil)

Emacs configuration for perl programming

Fri, 03 Mar 2023 00:00:00 +0000

Configuration taken from https://www.emacswiki.org/emacs/CPerlMode

;;; Perl
;; cperl-mode is preferred to perl-mode
;; "Brevity is the soul of wit" <foo at acm.org>
(defalias 'perl-mode 'cperl-mode)
(setq cperl-invalid-face nil) 
(setq cperl-electric-keywords t) ;; expands for keywords such as foreach, while, etc...
(setq cperl-hairy t) ;; Turns on most of the CPerlMode options

Python docstrings

Tue, 28 Feb 2023 00:00:00 +0000

In python, docstrings are used to define the functions documentation. Refer this page,

https://peps.python.org/pep-0257/


def function(a, b):
    """Do X and return a list."""

How-to delete an element from a xml tree in Python

Mon, 27 Feb 2023 00:00:00 +0000

Following are the steps to delete an element from a xml tree proprly when parsing with python,

https://stackoverflow.com/questions/47041688/remove-element-from-xml-with-elementtree

Example XML tree


<foo>
   <bar>
      <level>
         <test name="1">
            <stuff>
               hello
            </stuff>
         </test>
         <test name="2">
            <stuff>
               hello
            </stuff>
         </test>
      </level>   
   </bar>
</foo>

Python code to delete stuff


import xml.etree.ElementTree as ET

tree = ET.parse('myfile.xml')
root = tree.getroot()

for test in root.iter('test'):
    for stuff in test.findall('stuff'):
       test.remove(stuff)

print ET.tostring(root)

You need to have pointer to parent tag in order to remove child tag.

Fuzzy matching with python

Sun, 26 Feb 2023 00:00:00 +0000

Fuzzy matching is great. In fact, it is better than regular expression matching in certain cases. Come to think of it, our entire human brain works on fuzzy matching.

Take handwriting, for example, everyone can read each other’s handwriting as long as it’s legible. That’s fuzzy matching on an organic level.

I had a problem where I have a string of text, and I wanted to match the substring with other string but the issue is that the substring varies from string to string and I cant predict the proper substring to do a regex matching. So suddenly out of the blue I got an idea to do a fuzzy matching.

Adding epiog to python scripts using argparse module

Mon, 20 Feb 2023 00:00:00 +0000

https://docs.python.org/dev/library/argparse.html#argparse.RawDescriptionHelpFormatter

We can add epilog to argparse help and description to add more info. Refer link above.

PHP Notes

Mon, 20 Feb 2023 00:00:00 +0000

PHP Notes

Programming

Sun, 19 Feb 2023 00:00:00 +0000

Coding Guidelines

Sat, 18 Feb 2023 00:00:00 +0000

First rule of coding, do not code
Second rule of coding, write less code whenever you can

C++ notes

Fri, 17 Feb 2023 00:00:00 +0000

For loops

for (uint32_t i=0; i<10; i++) {
printf("i = %d", i);
}

Prints

printf(“unsigned = %u”, var1); printf(“signed = %d”, var1);

Functions

https://softwareengineering.stackexchange.com/questions/286490/what-is-the-difference-between-function-and-functionvoid 6.7.6.3 Function declarators (including prototypes) 10 The special case of an unnamed parameter of type void as the only item in the list specifies that the function has no parameters. 14 An identifier list declares only the identifiers of the parameters of the function. An empty list in a function declarator that is part of a definition of that function specifies that the function has no parameters. The empty list in a function declarator that is not part of a definition of that function specifies that no information about the number or types of the parameters is supplied.145)

ctags

Fri, 17 Feb 2023 00:00:00 +0000

Basics

Ctags is a tool that makes it easy to navigate large source code projects. It provides some of the features that you may be used to using in Eclipse or other IDEs, such as the ability to jump from the current source file to definitions of functions and structures in other files.

For full info refer this link, https://courses.cs.washington.edu/courses/cse451/10au/tutorials/tutorial_ctags.html

Commands

cd $REPO_ROOT
ctags -R *

In vim

:! ctag -R *

Add the tags file to vimrc

Documentation notes

Fri, 17 Feb 2023 00:00:00 +0000

Emacs lisp / elisp

Fri, 17 Feb 2023 00:00:00 +0000

(let ((messages-buffer (get-buffer "*Messages*")))
  (display-buffer-at-bottom messages-buffer
    '(display-buffer-pop-up-window
      (window-height . 0.2))))

General programming notes

Fri, 17 Feb 2023 00:00:00 +0000

File structure

Always try to keep files in one directory, but name them properly
Use multiple directories to dump similar data

json

Cannot use bash variables inside json files

Programming Concepts

Fri, 17 Feb 2023 00:00:00 +0000

Arrays
Associative arrays
dicts
case
while
for
if
exit codes and returns
advicing functions
Fuzzy matching - Fuzzy Matching with python

Programming quotes

Fri, 17 Feb 2023 00:00:00 +0000

How to shoot yourself in the foot

The problem with object-oriented languages is they’ve got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle. — Joe

Some people, when confronted with a problem, think ‘I know, I’ll use regular expressions.’ Now they have two problems.

Jamie Zawinski

Yuan-Ma said, ‘When you cut against the grain of the wood, much strength is needed. When you program against the grain of the problem, much code is needed.’

Advising a function in emacs lisp

Thu, 16 Feb 2023 00:00:00 +0000

One of the awesome things that I found when programming in elisp is the advice. For any function, you can advice before, after, around, to it.

When you advice a function A with a function B. Function B will executed before it. This is really interesting and useful.

(advice-add 'funa :before 'funb)

EMACS is a event based program, it has hooks, advices and all that goodness to modify and customize anything. 🪝

Bash

Thu, 16 Feb 2023 00:00:00 +0000

Bash

Reading materials

Select statement

select opt in y n; do
	echo $opt
done

This creates a loop where the user can select the option. Use case to break out of the loop.

select opt in y n; do
	echo $opt selected
	case $opt in
		y)
			break 
			;;
		n)
			break 
			;;
		*)
			echo wrong option
			;;
	esac
done

Bash variables

$USER
$HOSTNAME
$PS1

To Find or List all environment variables

env

This is useful when we want to manage the shell variables properly

VLSI

Thu, 16 Feb 2023 00:00:00 +0000

VLSI

How to shoot yourself in the foot

Tue, 07 Feb 2023 00:00:00 +0000

How to shoot yourself in the foot

Described below are several methods for shooting yourself in the foot using various programming techniques.

C
You shoot yourself in the foot.

C++
You accidentally create a dozen instances of yourself and shoot them all in the foot. Providing emergency medical care is impossible since you can’t tell which are bitwise copies and which are just pointing at others and saying, “That’s me over there.”

When to use implicit else

Mon, 12 Dec 2022 00:00:00 +0000

https://medium.com/lost-but-coding/when-to-use-implicit-else-e891cdcfe1bd

The author describes an ‘implicit else’. I’ve never heard of such a thing. Turns out it’s just doing this:

if (x) {
  return y;
 }
return z;

instead of this:

if (x) {
  return y;
 } else {
  return z;
 }

Is it ok to murder a program

Wed, 12 Oct 2022 00:00:00 +0000

I’ve been thinking about the life of humans in relation to the programs we write. Here are some examples,

Scenario 1

We assume that there is a law that allows murder if and only if you will make one offspring and raise it until it reaches the age of the murder victim.

Scenario 2

Let us assume that a person is on his/her deathbed, and you were given a knife. You are allowed to end the person’s suffering a day before the natural death. Will you do it? What if it was an hour before, a second before or a millisecond before. Will you still do it?

How to customize tmux status bar with shell scripts

Thu, 06 Oct 2022 00:00:00 +0000

TMUX status bar can be customized to run shell scripts.

In the .tmux.conf file, in the status left or right command execute the shell script using the following syntax,

set -g status-right '| #(shell_script.bash) |'

This will print the output of that shell script in the status bar. Useful if you want to check the size the home directory.

Contents of shell_script.bash example

#!/bin/bash

df -h $HOME | awk '{print $5}' | tail -n 1

Battery information in i3 status bar

Tue, 27 Sep 2022 00:00:00 +0000

First create battery block,

battery 0 {
  format = " %status %percentage %remaining "
  format_down = " no battery "  
  last_full_capacity = false
  integer_battery_capacity = true  
  hide_seconds = true    
  status_chr = ""
  status_bat = "☉"
  status_full = "☻"
  low_threshold = 10
  threshold_type = percentage
  path = "/sys/class/power_supply/BAT0/uevent"
}

then add it to the order array,

order += "battery 0"

Make sure to check the path of the battery first. In my case it was /sys/class/power_supply/BAT0/uevent. It might be different for other laptops.

How to find out what display server I am using

Thu, 15 Sep 2022 00:00:00 +0000

https://unix.stackexchange.com/questions/236498/how-to-get-information-about-which-display-server-is-running

ps -e | grep tty

Start your commands with a comma

Tue, 13 Sep 2022 00:00:00 +0000

https://rhodesmill.org/brandon/2009/commands-with-comma/

Programming on Raveen Kumar

Contacts Organizer cli app

Power of 2s

Reading notes - Designing a Video Game hardware in Verilog

Static timing anaysis

Emacs symbol search at point

Mark ring and Jumplist with emacs and helm

Stop asking tags table to be reset every time a new file is visited in a different project

Emacs configuration for perl programming

Python docstrings

How-to delete an element from a xml tree in Python

Fuzzy matching with python

Adding epiog to python scripts using argparse module

PHP Notes

PHP Notes

Programming

Coding Guidelines

C++ notes

For loops

Prints

Functions

ctags

Basics

Commands

Documentation notes

Emacs lisp / elisp

Open messages buffer in a popup window below

General programming notes

File structure

json

Programming Concepts

Programming quotes

Advising a function in emacs lisp

Bash

Bash

Reading materials

Select statement

Bash variables

To Find or List all environment variables

VLSI

VLSI

How to shoot yourself in the foot

How to shoot yourself in the foot

When to use implicit else

Is it ok to murder a program

How to customize tmux status bar with shell scripts

Battery information in i3 status bar

How to find out what display server I am using

Start your commands with a comma