LUA Language

Comments

-- comment
-- [[multi line comment]]

Output

io.write("string", 5, 4, "string", 3 ) -->"string54string3"
print("that ".."what") --> "das was"

String

name = "🅱️eter"
multiline = [[multiline string]]
longString = name .. multiline
string.format("Pi = %.10f", math.pi) --> Pi = 3.1415926535
string.len(name) --> returns length of string
#name--> returns length of string
string.gsub(name, "p", "me") --> Replaces every p with me in name
string.find(name, "p") --> 1, finds the first index of the searched term
string.upper(name) --> "PETER"
string.lower(name) --> "peter"
string.gmatch(name, "e") --> returns every match it finds in the string

Number

bigNum = 9223372036854775807 --> Biggest number possible in LUA
precision of up to 13 decimals
number = number + 1 --> Increment

Boolean

isAble = true

Nil

Everything is nil if it is not defined

Table

Description

Tables are key value paired list, can be used to create arrays, lists, and even used to implement OOP

Loops in LUA always start at index 1. So every table starts at index 1. You don’t have to follow this convention, it is possible to write onto the index 0. But it is recommended to use 1 as starting index.

Example

myTable = {}
#myTable -->  Number of items
 
for i = 1, 10 do 
 myTable[i] = i
end
 
-- same as
myTable = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }
 
-- same as
myTable = { [1]=1, [2]=2, [3]=3, [4]=4, [5]=5, [6]=6, [7]=7, [8]=8, [9]=9, [10]=10 }
 
print(myTable[1]) --> 1
table.insert(myTable, 1, 0)
print(myTable[1]) --> 0
 
print(table.concat(myTable, ", "))
 
table.remove(myTable, 1)
print(table.concat(myTable, ", "))

Type conversion

string --> tostring(variable)
number --> tonumber(variable)
table --> table.concat(variabel, ", ")

Relational Operators

Description

greater than >
smaller than <
same or greater >=
same or smaller <=
same == br
not same ~=

Example

age = 13
if age < 16 then
 print("you cant go to school")
 local localVar = 10
elseif (age <= 16) and (age < 18) then
 print("you cant drive")
else
 print("you can vote")
end

Logical Operators

and, or, not

age = 13
if (age < 14) or (age > 67) then print("you shouldnt work")
print(string.format("not true = %s", tostring(not true)))

Local

Description

local Variables are only accessible where defined

Example

function myFunc () 
 local myLocal = "local"
end
 
print(myLocal) --> nil

Math

Description

5+3 --> 8
5-3 --> 2
5*3 --> 15
5/3 --> 1.66666666666667
5%3 --> 2

Example

floor, ceil, max, min, sin, cos, tan, asin, acos, exp, log, log10, pow, sqrt, random, randomseed

Random numbers

math.random() -- number between 0 and 1
math.random(10) -- number between 1 and 10
math.random(5, 100) -- number between 5 and 100
math.randomseed(os.time()) -- good random value

Ternary operator

person = "hans"
 
evaluation = person == "hans" and "joe" or "mike"
print(jan) --> "joe"
 
evaluation = person == "michael" and "joe" or "mike"
print(jan) --> "mike"

Type checking

type(variable) --> returns type

Looping

i = 1
 
-- Asks first before executing code
while (i <= 10) do 
 print(i)
 i = i + 1
 
 if i == 8 then 
  break 
 end
end
 
-- Executes the code first before it asks
repeat
 print("Enter your guess : ")
 guess = io.read() 
until tonumber(guess) == 15
 
 
 
-- for loops, start at 1 go until 10, increment each time with 1
 
for i = 1, 10, 1 do
 print(i)
end
 
-- loop over tables
months = { "Jan", "Feb", "Mar", "Apr", "Jun", "Jul", "Aug", "Sep", "Oct", "Dec"}
 
for key, month in pairs(months) do
 print(month)
end

Multi table

Description

Nested Arrays, nested tables. These can be used as a representation of objects or more complex structures and not just tables.

Example

aMultiTable = { }
 
for i = 0, 9 do
 aMultiTable[i] = {}
 for j = 0, 9 do
  aMultiTable[i][j] = tostring(i) .. tostring(j)
 end
end
 
print("Table[1][2] : ", aMultiTable[1][2], "\n")
 
for key, value in pairs(aMultiTable) do
  print("Key " .. key)
  for scndKey, scndValue in pairs(value) do
    print("Value " .. scndValue)
  end
end 

Functions

Description

In LUA you define functions by using the keyword "function" followed by the name of the function and the parameters. Closing it with an end is necessary. Functions can return Values, more than 1 or 2. If you know the exact amount of returning values, you can prepare the variables to hold the value. But if there are dynamically values that are getting returned you will have to look into the next block -> dynamic return functions

In the example I used an regular expression, it makes it easier to filter for specific rules. Just like Phone numbers or other such things.

Example

function getSum(num1, num2)
 return num1 + num2
end
 
print(string.format("5 + 2 = ".. getSum(5,2)))
 
function splitStr(theString)
 stringTable = {}
 local i = 1
 for word in string.gmatch(theString, "[^%s]+") do
  stringTable[i] = word
  i = i + 1
 end
 
 return stringTable, i 
end
 
splitStrTable, numOfStr = splitStr("The Turtle")
 
for j = 1, numOfStr - 1 do
 print(string.format("%d : %s", j, splitStrTable[j]))
end

Input/Output

Description

There are some crucial commands for the io library:
io.close([file])
io.flush()
io.lines([filename])
io.output([file])
using the standard library and standard in and out, the files get closed automatically when you iterate over them with a for loop, so you don't have to manually call file.close()

Example

result, errmsg, errcode = io.lines("code.a51")

if (result ~= nil) then
  for line in result do
    print(line)
  end
end