helpers.lua

function string:split(delimiter)
  local result = { }
  local from  = 1
  local delim_from, delim_to = string.find( self, delimiter, from  )
  while delim_from do
    table.insert( result, string.sub( self, from , delim_from-1 ) )
    from  = delim_to + 1
    delim_from, delim_to = string.find( self, delimiter, from  )
  end
  table.insert( result, string.sub( self, from  ) )
  return result
end

function string:trim()
  return (self:gsub("^%s*(.-)%s*$", "%1"))
end

-- http://lua-users.org/wiki/TableSerialization
function table_print (tt, indent, done)
  done = done or {}
  indent = indent or 0
  if type(tt) == "table" then
    local sb = {}
    for key, value in pairs (tt) do
      table.insert(sb, string.rep (" ", indent)) -- indent it
      if type (value) == "table" and not done [value] then
        done [value] = true
        table.insert(sb, "{\n");
        table.insert(sb, table_print (value, indent + 2, done))
        table.insert(sb, string.rep (" ", indent)) -- indent it
        table.insert(sb, "}\n");
      elseif "number" == type(key) then
        table.insert(sb, string.format("\"%s\"\n", tostring(value)))
      else
        table.insert(sb, string.format(
            "%s = \"%s\"\n", tostring (key), tostring(value)))
       end
    end
    return table.concat(sb)
  else
    return tt .. "\n"
  end
end

function to_string( tbl )
    if  "nil"       == type( tbl ) then
        return tostring(nil)
    elseif  "table" == type( tbl ) then
        return table_print(tbl)
    elseif  "string" == type( tbl ) then
        return tbl
    else
        return tostring(tbl)
    end
end

-- https://gist.github.com/FGRibreau/3790217
table.filter = function(t, filterIter)
  local out = {}

  for k, v in pairs(t) do
    if filterIter(v, k, t) then out[k] = v end
  end

  return out
end

-- http://lua-users.org/wiki/FunctionalLibrary
-- e.g: map({1,2,3}, double)    -> {2,4,6}
table.map = function (tbl, func)
    local newtbl = {}
    for i,v in pairs(tbl) do
        newtbl[i] = func(v)
    end
    return newtbl
end