prettyPreAcc pp alvl wrap (FoldSeg f e acc1 acc2)
  = wrap 
  $ prettyArrOp "foldSeg" [parens (prettyPreFun pp alvl f), prettyPreExp pp 0 alvl parens e,
                           pp alvl parens acc1, pp alvl parens acc2]
prettyPreAcc pp alvl wrap (FoldSeg f e acc1 acc2)
  = wrap 
  $ prettyArrOp "foldSeg" [parens (prettyPreFun pp alvl f), prettyPreExp pp 0 alvl parens e,
                           pp alvl parens acc1, pp alvl parens acc2]
prettyPreAcc pp alvl wrap (FoldSeg f e acc1 acc2)
  = wrap 
  $ prettyArrOp "foldSeg" [parens (prettyPreFun pp alvl f), prettyPreExp pp 0 alvl parens e,
                           pp alvl parens acc1, pp alvl parens acc2]