izabera

namerefs (introduced in bash 4.0) act as aliases for other variables

var=meow
declare -n ref=var

echo $ref  # prints meow

ref=moo
echo $var  # prints moo

izabera

#if 0
#define _XOPEN_SOURCE 700
#include <aio.h>
#include <arpa/inet.h>
#include <assert.h>
#include <_Complex.h>
#include <ctype.h>
#include <dirent.h>
#include <dlfcn.h>
#include <errno.h>

izabera

set -f
IFS=

rpn () {
    for token do
        case $token in
            +|-|\*|/|%|\*\*) (( stack[-2] = stack[-2] $token stack[-1] )); unset stack[-1] ;;
            =) (( ${stack[-2]} = stack[-1] )); unset stack[-1] stack[-1] ;;
            *) stack+=($token) ;;
        esac

izabera

#include <arpa/inet.h>
#include <errno.h>
#include <netinet/in.h>
#include <pty.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/wait.h>

izabera

#!/bin/bash
pi=205667
scale=65536
maskf0=-$scale
mask0f=$((scale-1))
shift=16
pisq=42389628127
pi2=411775
pi_2=102944
pi_4=51472

izabera

for the latest chapter of what's becoming a blog on the most cursed bash you can imagine, let's do some maths together

euclid's algorithm for gcd could be written like this in python:

>>> def gcd(a, b):
...     if b:
...         return gcd(b, a%b)
... return a

izabera

{n=$1;r=n":";for(p=2;p*p<=n;p++)while(n%p==0){r=r" "p;n/=p}$1=n>1?r" "n:r}1

izabera

#!/bin/bash

printf %b%.b \
        '\e7'               'save cursor position' \
        '\e[9999;9999H'     'move to bottom right' \
        '\e[6n'             'get cursor position'  \
        '\e8'               'restore cursor'       \
        '\e[?u'             'kitty kbd proto'      \
        '\e[?2026$p'        'synchronised output'  \
        '\e[m'              'reset colours'        \

izabera

#!/bin/bash
a=({1..1000000})
TIMEFORMAT=%R

for mult in {1..100}; do
    printf "%s " "$mult"
    RANDOM=0
    time for i in {1..100000}; do
        : "${a[RANDOM*mult/10]}"
    done

izabera

#!/bin/bash

# max multiple of pi so our maths always fits in a signed 64 bit int
pi=314159
scale=100000



# bhaskara's formula
# https://en.wikipedia.org/wiki/Bh%C4%81skara_I's_sine_approximation_formula