thoughtpolice

      if thing then error "bad things" else 10*2

      let x = error "bad things" if thing then x else 10*2

      h <- openThing "foo"
      doStuff h
      ... some more stuff ...
      undoStuff h
      closeThing h

   I can change this to:

      let begin f =
        h <- openThing f
        doStuff h
      let end h =
        undoStuff h
        closeThing h

      h <- begin "foo"
      ... some more stuff ...
      end h

      let withThing x f = 
        h <- openThing f
        doStuff h
        f
        undoStuff h
        closeThing h

      let stuff = ... do some stuff ...

      withThing "foo" stuff

  ids := getAllUserIds  -- fetch from source 1 time
  foreach id as ids {
    x <- getUserFriends id -- N queries, 1 for each id
    ...
  }