func::[(Int,String)]
func =do
    a <- [1,2,3]
    b <- ["a","b"]
    return (a,b)

do
a <- [1,2,3]
b <- ["a","b"]
return (a,b)

[1,2,3] >>= (a -> do
  b <- ["a","b"]
  return (a,b) )

[1,2,3] >>= (a ->
  ["a","b"] >>= (b ->
     return (a,b) ))