table_ext.lua

require "underscore_alias"

_G.count = function (iter)
  return reduce(iter, 0, function (a, x) return a+1 end)
end

_G.sum = function (iter)
  return reduce(iter, 0, function (a, x) return a+x end)
end

-- Using sum+count would be two times slower and would consume the iterator
_G.mean = function (iter)
  local sum, count = 0, 0
  each(iter, function (x)
  sum = sum + x
  count = count + 1
  end)
  if count == 0 then
  return 0
  else
  return sum / count
  end
end

_G.count_pairs = function (iter)
  local n = 0
  for _ in pairs(iter) do
  n = n+1
  end
  return n
end

function table.sorted_pairs(t, order)
   -- collect the keys 
  local keys = {} 
  for k in pairs(t) do keys[#keys+1] = k end 

  -- if order function given, sort by it by passing the table and keys a, b, 
  -- otherwise just sort the keys  
  if order then 
  table.sort(keys, function(a,b) return order(t, a, b) end) 
  else 
  table.sort(keys) 
  end 

  -- return the iterator function 
  local i = 0 
  return function() 
  i = i + 1 
  if keys[i] then 
    return keys[i], t[keys[i]] 
  end 
  end 
end

function table.contains(tab, val)
  for k, v in pairs(tab) do
  if v == val then return true end
  end
  return false
end

function table:copy ()
  local t = {}
  for k, v in pairs(self) do
  t[k] = v
  end
  return t
end