prettyPreExp pp lvl alvl wrap (IndexHead ix)
  = wrap $ text "indexHead" <+> prettyPreExp pp lvl alvl parens ix
prettyPreExp pp lvl alvl wrap (IndexHead ix)
  = wrap $ text "indexHead" <+> prettyPreExp pp lvl alvl parens ix
prettyPreExp pp lvl alvl wrap (IndexHead ix)
  = wrap $ text "indexHead" <+> prettyPreExp pp lvl alvl parens ix