BIT returns a result that is the bit value of x, and has
a length specified by y.
>>-BIT(x-+----+-)---------------------------------------------->< '-,y-'
- x
- Expression.
- y
- Expression. If necessary, y is converted to a real fixed-point binary value. If y is omitted, the length is determined by the rules for type conversion. If y = 0, the result is the null bit string. y must not be negative.