= Lua
== String library functions (5.4)

> for k,v in pairs(string) do print(k) end
byte
char
dump
find         if you need the first match and its position
format
gmatch       if you are interested in matches and want to iterate over them
gsub         if you substitute the matches ignoring their position
match        if you need all captures from the first match
len
lower
pack
packsize
rep
reverse
sub
unpack
upper

== metatable methods

https://gist.github.com/oatmealine/655c9e64599d0f0dd47687c1186de99f

__add(a, b)
__sub(a, b)
__mul(a, b)
__div(a, b)
__unm(a)
__mod(a, b)	Lua 5.1
__pow(a, b)	Lua 5.1
__idiv(a, b)	Lua 5.3

__band(a, b)	Lua 5.3
__bor(a, b)	Lua 5.3
__bxor(a, b)	Lua 5.3
__bnot(a)	Lua 5.3
__shl(a, b)	Lua 5.3
__shr(a)	Lua 5.3

__eq(a, b)
__lt(a, b)
__le(a, b)

__concat(a, b)
__len(a)	Lua 5.1

__index(self, k)
__newindex(self, key, value)
__call(args)
__mode
__close(value, err?)	Lua5.4
__gc()

__tostring()
__metatable
__name
__pairs

== iterators

-- example for an iterator
-- NOTE: if your iterator handles tables, you might be interested in “next_key, next_value = next(tbl, previous_key)” or “nextval“ functions
local steps = function (start, stop, step_by)
  local iter = start
  return function ()
    local current = iter
    if current < stop then
      iter = iter + (step_by or 1)
      return current
    else
      return nil
    end
  end
end

for i in steps(3, 7, 1) do
  print(i)
end