sliceToPred path (SliceProper lower upper Nothing _) =
    pSliceProper <$>
        maybeExprToPred (path.slice_lowerL) lower <*>
            maybeExprToPred (path.slice_upperL) upper <*>
                return isNothing
sliceToPred path (SliceProper lower upper Nothing _) =
    pSliceProper <$>
        maybeExprToPred (path.slice_lowerL) lower <*>
            maybeExprToPred (path.slice_upperL) upper <*>
                return isNothing
sliceToPred path (SliceProper lower upper Nothing _) =
    pSliceProper <$>
        maybeExprToPred (path.slice_lowerL) lower <*>
            maybeExprToPred (path.slice_upperL) upper <*>
                return isNothing