lua-exmpls's Introduction

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data types

Bools

Booleans are represented by true and false.
Everything is considered truthy, except false and nil. Empty tables, strings, 0 evaluate to True, if used in if/else condition.

Strings

Concatenate two strings using .. (two dots) i.e. "hello" .. "world"

Tables

tables are created using {}
tables can be array like {1, 2, 3, 4} or a dictionary (or map) like {a=1, b=2} or both like {1, 2, 3, a=1, b=2}
tables can be nested like {1, 2, {1, 2, {a=1}}}
Elements from tables can be extracted by (assuming t = {1, 2, a=1})
- dot syntax i.e. t.a
- using square brackets with:
  - key name e.g. t["a"]
  - array index e.g. t[1]
- Only array elements have the index, key-value pairs don't
- arrays are 1 indexed (not zero)

Control Structures

if/else

if/else syntax:

if <condition> then
    <do something>
elseif <condition> then
    <do something else>
else
    <do something>
end

# or
if <condition> then <do something> end
if <condition> then <do something> else <do something else> end

while

while syntax:

local i = 1
while i <= 10 do
    print(i)
    i = i + 1
end

repeat until

repeat until syntax:

local i = 1
repeat
    print(i)
    i = i + 1
until i > 10

Repeat a statement until a condition is true.

In Lua the scope of a local variable declared inside the loop includes the condition.

local x = 100
local sqrt = x / 2
repeat
  sqrt = (sqrt + x / sqrt) / 2
  local error = math.abs(sqrt ^ 2 - x)
until error < x / 10000 -- the local error defined above is visible here

functions

  x = function(param)
      <do something>
  end

Scopes

You created variables in local scope using local keyword e.g. local var = 1
By default, if variables are created without local keyword, then variables are created in global scope

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