**Use case**

Convert bitmask to position.
It would allow us to directly use FLAT dictionary or Enum datatype without jumping around slow `bitmasktoArray` and `arrayMap`

**Describe the solution you'd like**

```
SELECT
    arrayMap(x -> log2(x), bitmaskToArray(100)) AS bitmask,
    bitPositions(100)  AS bitpositions

┌─bitmask─┬─bitpositions─┐
│ [2,5,6] │ [2,5,6]      │
└─────────┴──────────────┘
```

}
                res_offsets[row] = res_values.size();
            }
            out_column = ColumnArray::create(std::move(col_values), std::move(col_offsets));
            return true;
        }
        else
        {
            return false;
        }
    }
    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t ) const override
    {
        const IColumn * in_column = arguments[0].column.get();
        ColumnPtr out_column;
        if (tryExecute<UInt8>(in_column, out_column) ||
            tryExecute<UInt16>(in_column, out_column) ||
            tryExecute<UInt32>(in_column, out_column) ||
            tryExecute<UInt64>(in_column, out_column) ||
            tryExecute<Int8>(in_column, out_column) ||
            tryExecute<Int16>(in_column, out_column) ||
            tryExecute<Int32>(in_column, out_column) ||
            tryExecute<Int64>(in_column, out_column))
            return out_column;
        throw Exception("Illegal column " + arguments[0].column->getName()
                        + " of first argument of function " + getName(),
                        ErrorCodes::ILLEGAL_COLUMN);
    }
};
class FunctionToStringCutToZero : public IFunction