hugonotes

Links

Sat, 02 Oct 2021 10:10:12 +0200

Technical

Mobile

The Search for a FLOSS Mobile OS (Aug 2021) https://blog.emacsen.net/blog/2021/08/23/floss-mobile-os-aug-2021/ https://news.ycombinator.com/item?id=28296738

Programming

Data Structures and Algorithms in JavaScript https://news.ycombinator.com/item?id=20634409 https://amejiarosario.gumroad.com/l/dsajs

John Carmack on Functional Programming (2013 https://news.ycombinator.com/item?id=15036591

A Thought Experiment: Using the ECS Pattern Outside of Game Engines https://news.ycombinator.com/item?id=21892126 https://adventures.michaelfbryan.com/posts/ecs-outside-of-games/ https://en.m.wikipedia.org/wiki/Entity_component_system#Characteristics

Web

HTML, CSS

Scrollspy with ‘just JavaScript’ https://medium.com/p1xts-blog/scrollspy-with-just-javascript-3131c114abdc

TypeSafe CSS https://uglyduck.ca/typesafe-sans-css/

Ten modern layouts in one line of CSS https://web.dev/one-line-layouts/ https://news.ycombinator.com/item?id=24003385

My current HTML boilerplate https://www.matuzo.at/blog/html-boilerplate/ https://news.ycombinator.com/item?id=26952557

HTML5 Boilerplate https://html5boilerplate.com/

A simple guide to HTML <head> elements https://github.com/joshbuchea/HEAD

HTML Tips (2020) https://markodenic.com/html-tips/ https://news.ycombinator.com/item?id=27054348

Drop-in CSS Frameworks https://github.com/sw-yx/spark-joy#cssui-templates

Installing Arch Linux on a VPS

Fri, 01 Oct 2021 18:21:42 +0200

1. Base system

Create VPS, pick Debian 9.3 as OS.

-→ didn’t work 2nd time, stuck in 1st reboot: picked centos and worked

Copy bootstrap files from M:\vm\isovps2arch to M:\mshare\vps2arch and cd into the latter folder.

Upload bootstrap files to the newly created VPS:

scp * root@IP_ADDRESS:

Log into the VPS

chmod +x vps2arch
mv * / && cd /
./vps2arch
echo HOSTNAME > /etc/hostname
sync; reboot -f

2. Create user

useradd -m bert
groupadd sudoers
usermod -aG sudoers bert
passwd bert

pacman -Syu sudo vim ufw knockd lighttpd git

Installing Arch Linux in VirtualBox

Fri, 01 Oct 2021 18:18:58 +0200

1. Arch Linux .iso file

archlinux-2018.02.01-x86_64.iso: from: https://archlinux.cu.be/iso/2018.02.01/archlinux-2018.02.01-x86_64.iso saved at: "M:vmisoarchlinux-2018.02.01-x86_64.iso"

2. VirtualBox:

This document applies to v5.2.6
Help/About VirtualBox

File/Check for updates
in File/Preferences
General: check vm default location: "M:vm"
in File/Host Network Manager
+

Create host-only network

Set the IP address, e.g. : 192.168.236.2

Network mask : 255.255.255.0
new vm
+

name: yeba

make sure "M:vmyeba" doesn’t exist before creation of VM

type/version: arch linux 64 bit

memory 4096 MB

create virtual HD

press "create"

File size 30 GB

VDI

dynamically allocated

Installing Arch Linux on a PC

Fri, 01 Oct 2021 18:17:19 +0200

This guide explains how to install vanilla Arch Linux on a PC.

Prerequisites

A PC or a laptop, with
a USB port

wifi adapter

a HDD with contents that are no longer needed
A USB stick with contents that are no longer needed.
A PC with a working operating system and internet access. This may also be the machine we will install Arch Linux on. We will assume a Linux(-like) environment with 'curl' and 'dd'

Exercise 1.07

Fri, 01 Oct 2021 15:49:32 +0200

Background: Section 1.1.7, Square Roots by Newton’s Method

(define (square x) (* x x))

(define (average x y)
  (/ (+ x y) 2))

(define (improve guess x)
  (average guess (/ x guess)))

(define (good-enough? guess x)
  (< (abs (- (square guess) x)) 0.001))

(define (sqrt-iter guess x)
  (if (good-enough? guess x)
      guess
      (sqrt-iter (improve guess x)
                 x)))

(define (sqrt x)
  (sqrt-iter 1.0 x))

Question:

The good-enough? test used in computing square roots will not be very effective for finding the square roots of very small numbers. Also, in real computers, arithmetic operations are almost always performed with limited precision. This makes our test inadequate for very large numbers. Explain these statements, with examples showing how the test fails for small and large numbers. An alternative strategy for implementing good-enough? is to watch how guess changes from one iteration to the next and to stop when the change is a very small fraction of the guess. Design a square-root procedure that uses this kind of end test. Does this work better for small and large numbers?

Exercise 1.06

Fri, 01 Oct 2021 15:48:01 +0200

Background: Section 1.1.7, Square Roots by Newton’s Method

(define (square x) (* x x))

(define (average x y)
  (/ (+ x y) 2))

(define (improve guess x)
  (average guess (/ x guess)))

(define (good-enough? guess x)
  (< (abs (- (square guess) x)) 0.001))

(define (sqrt-iter guess x)
  (if (good-enough? guess x)
      guess
      (sqrt-iter (improve guess x)
                 x)))

(define (sqrt x)
  (sqrt-iter 1.0 x))

Question:

Alyssa P. Hacker doesn’t see why if needs to be provided as a special form. "Why can’t I just define it as an ordinary procedure in terms of cond?" she asks. Alyssa’s friend Eva Lu Ator claims this can indeed be done, and she defines a new version of if:

Exercise 1.05

Fri, 01 Oct 2021 15:46:39 +0200

Question:

Ben Bitdiddle has invented a test to determine whether the interpreter he is faced with is using applicative-order evaluation or normal-order evaluation. He defines the following two procedures:

(define (p) (p))

(define (test x y)
  (if (= x 0)
      0
      y))

Then he evaluates the expression

(test 0 (p))

What behavior will Ben observe with an interpreter that uses applicative-order evaluation? What behavior will he observe with an interpreter that uses normal-order evaluation? Explain your answer. (Assume that the evaluation rule for the special form if is the same whether the interpreter is using normal or applicative order: The predicate expression is evaluated first, and the result determines whether to evaluate the consequent or the alternative expression.)

Exercise 1.04

Fri, 01 Oct 2021 15:43:40 +0200

Question:

Observe that our model of evaluation allows for combinations whose operators are compound expressions. Use this observation to describe the behavior of the following procedure:

(define (a-plus-abs-b a b)
    ((if (> b 0) + -) a b))

Answer:

In the body of a-plus-abs-b a b, the expression (if (> b 0) + -) evaluates to an arithmetic operation (either + or -, depending on the sign of b’s actual argument). The interpreter obtains a primitive procedure that it applies to the arguments replacing the formal parameters `a and b.

Exercise 1.03

Fri, 01 Oct 2021 15:42:25 +0200

Question:

Define a procedure that takes three numbers as arguments and returns the sum of the squares of the two larger numbers.

Answer:

(define (square x) (* x x))

(define (sum-of-squares x y) (+ (square x) (square y)))

(define (sum-squares-larger a b c)
    (cond ((and (<= a b) (<= a c)) (sum-of-squares b c))
          ((and (<= b a) (<= b c)) (sum-of-squares a c))
          (else (sum-of-squares a b))))

Exercise 1.02

Fri, 01 Oct 2021 15:38:53 +0200

Question:

todo

(+ 1 2)

Answer:

todo

Exercise 1.01

Fri, 01 Oct 2021 15:34:34 +0200

Question:

Below is a sequence of expressions. What is the result printed by the interpreter in response to each expression? Assume that the sequence is to be evaluated in the order in which it is presented.

10
(+ 5 3 4)
(- 9 1)
(/ 6 2)
(+ (* 2 4) (- 4 6))
(define a 3)
(define b (+ a 1))
(+ a b (* a b))
(= a b)
(if (and (> b a) (< b (* a b)))
    b
    a)
(cond ((= a 4) 6)
      ((= b 4) (+ 6 7 a))
      (else 25))
(+ 2 (if (> b a) b a))
(* (cond ((> a b) a)
         ((< a b) b)
         (else -1))
   (+ a 1))

Minecraft tips

Fri, 01 Oct 2021 14:13:46 +0200

Hoofden zetten

Plaats het hoofd van SpelerNaam in je inventaris: :

/give @p skull 1 3 {SkullOwner:"SpelerNaam"}

Plaats het hoofd van een ghast in je inventaris: :

/give @p skull 1 3 {SkullOwner:"MHF_Ghast"}

Voor andere mobs: vervang MHF_Ghast door: :

MHF_Alex
MHF_Blaze
MHF_CaveSpider
MHF_Chicken
MHF_Cow
MHF_Creeper
MHF_Enderman
MHF_Ghast
MHF_Golem
MHF_Herobrine
MHF_LavaSlime
MHF_MushroomCow
MHF_Ocelot
MHF_Pig
MHF_PigZombie
MHF_Sheep
MHF_Skeleton
MHF_Slime
MHF_Spider
MHF_Squid
MHF_Steve
MHF_Villager
MHF_WSkeleton
MHF_Zombie

Blokken: :

MHF_Cactus
MHF_Cake
MHF_Chest
MHF_CoconutB
MHF_CoconutG
MHF_Melon
MHF_OakLog
MHF_Present1
MHF_Present2
MHF_Pumpkin
MHF_TNT
MHF_TNT2

Babs

Fri, 01 Oct 2021 14:11:28 +0200

Introduction

babs, (an acronym for "babs: a build system") is a set of Makefiles meant to easily compile & link a set of interdependent modules, containing C/C++ source code, binaries like object files, static or dynamic libraries, etc …

Environment variables

In order to do its work, babs needs 3 environment variables:

BABS_DIR : the directory where the babs build system is located.
SOURCE_DIR : the directory where the source modules are located.
BUILD_DIR : the directory where all target and intermediate files are saved during the build process.

Headless install of Arch Linux on Raspberry Pi Zero W

Fri, 01 Oct 2021 14:06:50 +0200

Prerequisites

Arch Linux, with the following packages: dosfstools wpa_supplicant

Micro SD card

USB stick with slot for Micro SD Card

Raspberry Pi Zero W

Create an Arch Linux ARM system

TODO : chroot binfmt qemu

Partition Micro SD Card

In Linux, list the available devices: :

sudo fdisk -l

If Linux is running inside VirtualBox, consult the list of devices in: Devices>USB

Insert the Micro SD card in the USB adapter, and insert the adapter in a USB port.

Syntax highlighting

Fri, 01 Oct 2021 14:03:26 +0200

C++ program

#include <iostream>

using namespace std;

int main()
{
  cout << "Hello world!" << endl;
  return 0;
}

C program

#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>


int main(int argc, char **argv)
{
  void *handle;
  char *error;
  void (*fun)();
  char fileName[300];
  char* buildDir = getenv("BUILD_DIR");

  sprintf(fileName, "%s/toolkit/libtoolkit.so.1.0.0", buildDir);
  printf("fileName = %s\n", fileName);

  printf("mark1\n");

  dlerror();
  handle = dlopen ( fileName , RTLD_LAZY);
  if (!handle) {
      fputs (dlerror(), stderr);
        printf("\n");
      exit(1);
  }

  printf("mark2\n");

  fun = (void (*)()) dlsym(handle, "testfun1");
  if ((error = dlerror()) != NULL)  {
      fputs(error, stderr);
        printf("\n");
      exit(1);
  }

  printf("mark3\n");

  (*fun)();

  printf("mark4\n");

  dlclose(handle);

}

Android

Fri, 01 Oct 2021 13:54:23 +0200

Nexus 10

Boot in recovery mode

https://www.android.gs/how-to-boot-google-nexus-10-recovery-mode/

Reset to factory defaults

https://www.android.gs/how-to-hard-reset-the-google-nexus-10/

Cheatsheet

Fri, 01 Oct 2021 13:26:18 +0200

Check folder size:

du -sh foldername/

Clear trash folder (Ubuntu & friends):

rm -rf ~/.local/share/Trash/files ~/.local/share/Trash/info

Arch Linux guest VM in VirtualBox:

Restore networking:

sudo ip link set enp0s8 down && sudo ip link set enp0s8 up && curl www.google.com

Mount USB drive

Before inserting the USB drive, show list of devices: :

sudo lsblk -f

Insert USB drive, and select device in VirtualBox GUI menu ( Devices > USB > … )

Asciidoc markup

Fri, 01 Oct 2021 10:37:14 +0200

Text formatting

Description	Syntax	Result	Remark
Emphasis, quotes	`One 'Two' Three`	One 'Two' Three
Emphasis, underscores	`One Two Three`	One Two Three
Emphasis, quotes, unconstrained	`One''Two''Three`	One''Two''Three
Emphasis, underscores, unconstrained	`OneTwoThree`	OneTwoThree
Strong	`One Two Three`	One Two Three
Strong, unconstrained	`OneTwoThree`	OneTwoThree
Monospace	`One Two Three`	One Two Three
Monospace, unconstrained	`OneTwoThree`	OneTwoThree
Single quote	One `Two´ Three	One `Two´ Three	Doesn’t seem to work
Double quotes	One ``Two´´ Three	One ``Two´´ Three	Doesn’t seem to work
Single quote, unconstrained	One``Two´´Three	One``Two´´Three	Doesn’t seem to work
Unquoted	`One Two Three`	One Two Three	Meant to add inline attributes (see next line)
Colored text	`One Two Three`	One Two Three
Colored background	`One Two Three`	One Two Three
Big text	`One Two Three`	One Two Three
Underlined text	`One Two Three`	One Two Three
Overlined text	`One Two Three`	One Two Three
Line-through text	`One Two Three`	One Two Three
Combinations	`One Two Three`	One Two Three
Combinations, unconstrained	`OneTwoThree`	OneTwoThree
Big text	`One Two Three`	One Two Three
Superscript	`One ^Two Three`	One ^Two Three
More superscript	`One^TwoThree`	One^TwoThree
Subscript	`One _Two Three`	One _Two Three
More subscript	`One_TwoThree`	One_TwoThree

Install Void Linux on virt-manager

Mon, 01 Jan 0001 00:00:00 +0000

Sources

Goals

Host OS: Void Linux
Virtualization software: Virtual Machine Manager (virt-manager)
Guest OS: Void Linux
- Hostname: vogu
- One non-root user with sudo rights, named me
- Network access through the host system
- Dotfiles, with custom built Suckless tools: dwm, st, dmenu
- Development tools: python, nodejs, gcc, clang, neovim, zig
- Webservers etc running in the VM are reachable from the host system

Prerequisites

A running Void Linux host system
The folllowing Void Linux live .iso: https://repo-default.voidlinux.org/live/current/void-live-x86_64-20250202-base.iso

Install Void Linux on VirtualBox

Mon, 01 Jan 0001 00:00:00 +0000

Sources

https://linuxiac.com/void-linux-installation/

https://techviewleo.com/install-void-linux-on-virtualbox-vmware-workstation/

https://docs.voidlinux.org/installation/guides/chroot.html

Goals

Host OS: Windows
Virtualization software: VirtualBox
Guest OS: Void Linux
- Hostname: vivo
- One non-root user with sudo rights, named me
- Network access through the host system
- A tiling window manager: dwm
- Development tools: python, nodejs, gcc, clang, neovim
- Webservers etc running in the VM are reachable from the host system

Prerequisites

VirtualBox: https://www.virtualbox.org/
A Linux live .iso file, like for instance the ``Void Linux libc base'' one: https://repo-default.voidlinux.org/live/current/void-live-x86_64-20230628-base.iso

Installing Arch Linux on a Hetzner VPS

Mon, 01 Jan 0001 00:00:00 +0000

Boot live iso

In the web config panel of the VPS, mount the Arch Linux .iso in your server & reboot. Connect to the server with the web console.

loadkeys be-latin1

Network should work: :

curl www.google.com

Syncronize the system clock with NTP :

timedatectl set-ntp true

Create partition table :

fdisk -l /dev/sda

fdisk /dev/sda

First, create a partition (sda1) of size 32 MB (+32M). Change its type to 1 (EFI System). Then, create a partion (sda2) with the rest of the available space.