Scientific Computing

Appendix - Commands

Python

• Python can be used within the Python prompt, prefixed with >>>, or via .py files.
• Python is used to conduct computations.
• Versus a calculator, it supports arithmetic, comparisons, code reuse, and repeated actions.

\[ f(x) = \begin{cases} 9x^2 + 5 & x < 4 \\ 9 & 4 \leq x \leq 8 \\ 2 - x & x > 8 \end{cases} \]

def f(x):
    if (x < 4):
        return 9 * x ** 2 + 5
    elif (4 <= x <= 8):
        return 9
    elif (x > 8):
        return 2 - x

• Find \(f(x)\) for each of the following \(x\) values: \[ \{-1, 4, 5, 8, 11\} \]

result = []
for x in [-1, 4, 5, 8, 11]:
    result = result + [f(x)]
result

[14, 9, 9, 9, -9]

Neovim

• Use nvim to access a modal text editor.
• In i or insert mode, is like other editors.
• Outside i there’s “motions”, “operators”, “commands”
  • “Motions” move the cursor - where you would type in i mode
  • “Operators” manipulate text - add, delete, yank (copy), paste
  • “Commands” load and save files and exit Neovim.

Motion	Movement
h	left one character
j	down one line
k	up one line
l	right one character
0	beginning of line
$	end of line
/search_term	go to next occurance of “search_term”
e	end of word
b	beginning of word

Operator	Action
i	insert text
r	replace character
d	delete text, combined with a motion
y	yank text, combined with a motion
p	paste yanked text

Command	Action
:saveas file.txt	save text as “file.txt”
:w	save file
:x	save and exit
:q!	exit without saving

Bash

• Bash commands are used folder-relative.
• Bash is used within a terminal and is the default terminal environment.
• To get bash running:
  • Windows: Check Appendix - Git Bash
  • MacOS: Spotlight menu -> “Terminal” (zsh, but close enough)
• Mostly used to navigate the file system, organize files, launch programs like Python and Neovim

Command	Action
ls	list files in folder
rm f.txt	delete file “f.txt”
mkdir dir	create a new folder named “dir”
mv f.txt dir	move file “f.txt” to folder “dir”
pwd	print current folder
cd dir	change current folder to “dir”
cd ..	go to “parent” folder
echo hi	print the text “hi”
echo hi >f.txt	write “hi” to file “f.txt”
cat f.txt	see the text in f.txt