prettyPreAcc pp alvl wrap (Backpermute sh p acc)
  = wrap 
  $ prettyArrOp "backpermute" [prettyPreExp pp 0 alvl parens sh,
                               parens (prettyPreFun pp alvl p),
                               pp alvl parens acc]
prettyPreAcc pp alvl wrap (Backpermute sh p acc)
  = wrap 
  $ prettyArrOp "backpermute" [prettyPreExp pp 0 alvl parens sh,
                               parens (prettyPreFun pp alvl p),
                               pp alvl parens acc]
prettyPreAcc pp alvl wrap (Backpermute sh p acc)
  = wrap 
  $ prettyArrOp "backpermute" [prettyPreExp pp 0 alvl parens sh,
                               parens (prettyPreFun pp alvl p),
                               pp alvl parens acc]