Antlr.Runtime.BitSet.BitMask C# (CSharp) Method

        private static ulong BitMask( int bitNumber )
        {
            int bitPosition = bitNumber & MOD_MASK; // bitNumber mod BITS
            return 1UL << bitPosition;
        }

        public void Remove(int el)
        {
            int index = BitSet.WordNumber(el);

            if (index >= this._bits.Length)
            {
                return;
            }
            this._bits[index] &= ~BitSet.BitMask(el);
        }