mohit2152sharma / lua-exmpls

lua in one page

Note

Work in progress

• Add examples
• Add more details

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