[BREAKING] Simplify URL paths

content/drafts/lua.md

@@ -0,0 +1,191 @@
+---
+Status: Planned
+Created by: Trude EH
+tags:
+  - notes
+  - programming
+author: TrudeEH
+draft: true
+searchHidden: false
+showToc: true
+title: Lua
+---
+Embedded language.  
+  #todo 
+
+## Comments
+
+```Lua
+-- One-Line comment
+--[[ Multi-line
+      comment
+--]]
+```
+
+## Simple Literals
+
+```Lua
+local number = 5
+local string = "hello, world"
+local single = 'same as using \"'
+local multiline = [[ Multi
+line
+string ]]
+local yes, no = true, false
+local nothing = nil
+```
+
+## Functions
+
+Functions can be stored as values.
+
+```Lua
+local function hello(name)
+	print("Hello", name)
+end
+local greet = function(name)
+	-- .. is string concaternation
+	print("Hello " .. name .. "!")
+end
+-- Calling a function
+greet("Trude")
+greet "Trude"
+```
+
+Functions can also return other functions.
+
+```Lua
+local high = function(value)
+	return function(value2)
+		return value + value2
+	end
+end
+local add_one = high(1)
+print("1 + 2 -> ", add_one(2))
+```
+
+Functions can return multiple values.
+
+```Lua
+local return_four_values = function()
+	return 1, 2, 3, 4
+end
+first, second, third = return_four_values() -- "4" was discarded.
+```
+
+Variable arguments.
+
+```Lua
+local variable_arguments = function( ... )
+	local arguments = { ... }
+	for i, v in ipairs({ ... }) do print(i, v) end
+end
+print(variable_arguments("this", "is", "a", "test"))
+```
+
+## Tables
+
+Lua's only data structure. (Also used for maps and lists)
+
+### As lists…
+
+```Lua
+local list = { "first", 2, false, function() print("Fourth") end }
+print("Lua is 1-indexed:", list[1])
+```
+
+### As maps…
+
+```Lua
+local t = {
+	literal_key = "a string",
+	["an expression"] = "also works",
+	[function() end] = true
+}
+print("literal_key     : ", t.literal_key)
+print("an expression   : ", t["an expression"]
+print("function() end  : ", t[function() end]) -- nothing will be printed here, because each function definition points to a different memory address.
+```
+
+### Colon Functions
+
+```Lua
+local T = {}
+function T.something(self, ... ) end
+function T:something( ... ) end -- Same as the previous line
+```
+
+### Metatables
+
+```Lua
+local vector_mt = {}
+vector_mt.__add = function(left, right)
+	return setmetatable({
+		left[1] + right[1],
+		left[2] + right[2],
+		left[3] + right[3]
+	}, vector_mt)
+end
+local v1 = setmetatable({ 3, 1, 5 }, vector_mt)
+local v2 = setmetatable({ -3, 2, 2}, vector_mt)
+local v3 = v1 + v2 -- normally would produce an error, but doesn't, since the __add keyword was used.
+print(v3[1], v3[2], v3[3])
+```
+
+## Control Flow
+
+### For
+
+#### Lists
+
+```Lua
+local favs = { "ThePrimeagen", "ctt", "NoBoilerplate" }
+for index = 1, \#favs do -- # is the length operator (does not work on maps!)
+	print(index, favs[index])
+end
+for index, value in ipairs(favs) do -- ipairs return the index and values of that index
+	print(index, value)
+end
+```
+
+#### Maps
+
+```Lua
+local favs = { ThePrimeagen = 9.5, NoBoilerplate = "N/A" }
+for key, value in pairs(favs) do -- pairs return the index and values of that key
+	print(key, value)
+end
+```
+
+### If
+
+```Lua
+local function action(visit_page)
+	if visit_page then
+		print("Opening new tab...")
+	else
+		print("Skipping...")
+	end
+end
+-- "falsey": nil, false
+action() -- Same as: action(nil)
+action(false)
+-- Everything else is "truthy"
+action(true)
+action(0)
+action({})
+```
+
+## Modules
+
+Modules are just files.
+
+```Lua
+-- module.lua
+local M = {}
+M.some_function = function() end
+return M
+-- main.lua
+local something = require("module")
+something.some_function()
+```