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f(std::vector<bool, std::allocator<bool>> const&, unsigned long):
        mov     rax, rdi                    ; rax = v
        mov     rdi, rsi                    ; rdi = i
        mov     ecx, esi			        ; rcx = i
        mov     rdx, QWORD PTR [rax]	    ; rdx = *v
        shr     rdi, 6				        ; rdi >>= 6
        mov     eax, 1				        ; rax = 1
        sal     rax, cl				        ; rax <<= (rcx & 0xFF)
        and     rax, QWORD PTR [rdx+rdi*8]	; rax &= rdx[rdi]
        setne   al				            ; al = (rax != 0)

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These are simplified examples I came up with to go along with William Woodruff's excellent blog post on x86-64 addressing modes.

All the examples are compiled with GCC -O3 or -Os, which is indicative of what the compiler thinks the best option is in practice.

Base + Index

Use case: Indexing into a byte array (whose address is not fixed)

char f(char buf[], int index)

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library(tidyverse)

# find duplicates by col
df %>% filter(n() > 1, .by = "col")

# drop duplicates by col
df %>% distinct(col)

# summarize per group by
mtcars %>% 

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x86-32 cdecl

Arguments pushed on stack, right-to-left.

Caller-saved: eax, ecx, edx. All others are callee-saved.

Return value in eax.

General purpose registers:

1. EAX (Accumulator)

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# Horizontal bar chart, ordered by value
ggplot(df, aes(x = reorder(name, value), y = value)) + 
  geom_bar(stat = "identity") + 
  labs(title = "Title", x = "Name", y = "Value") +
  scale_y_continuous(expand = c(0,0)) + 
  coord_flip() + 
  theme_light()

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import pandas as pd

### Data import ###

# https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.to_csv.html 
df = pd.read_csv("file.csv")  


### Data types ###

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-- Syntax order
-- https://learn.microsoft.com/en-us/sql/t-sql/queries/select-transact-sql

WITH cte AS (cte_query)
SELECT cols
FROM table 
WHERE cond
GROUP BY col
HAVING cond
WINDOW window_expr

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# push to new github repo
git remote add origin git@github.com:jxu/repo.git  # use set-url if already set
git push -u origin master

# check out a remote branch
git fetch
git branch -v -a  # list all branches
git switch branchname

# change remote a branch is tracking

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" Custom vim config with my comments 
" (mostly from the ultimate Vim config amix/vimrc)

" => General
set nocompatible                " Disable compatibility mode
set history=1000                " Save more commands
set autoread                    " Read file when changed externally
set autowrite                   " Autosave before commands like :make
set noswapfile                  " No more .swp!

jxu

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