prettyPreAcc pp alvl wrap (Fold f e acc)
  = wrap 
  $ prettyArrOp "fold" [parens (prettyPreFun pp alvl f), prettyPreExp pp 0 alvl parens e,
                        pp alvl parens acc]
prettyPreAcc pp alvl wrap (Fold f e acc)
  = wrap 
  $ prettyArrOp "fold" [parens (prettyPreFun pp alvl f), prettyPreExp pp 0 alvl parens e,
                        pp alvl parens acc]
prettyPreAcc pp alvl wrap (Fold f e acc)
  = wrap 
  $ prettyArrOp "fold" [parens (prettyPreFun pp alvl f), prettyPreExp pp 0 alvl parens e,
                        pp alvl parens acc]