Object attributes

Attributes may be used to retrieve information about an object or an expression. For expression X:

X'size returns the number of bits in X
X'msb returns the value of the most significant bit of X
X'meta returns 1 if X contains metadata, and 0 otherwise
X'offset returns the offset of X, in bits, when X is an array element or structure member. If X evaluates to a stream, it instead returns the current location in that stream
X'last returns a previous value of the operand

These attributes are actually postfix operators, and their use is therefore not restricted to objects. They may be used anywhere where a postfix operator is allowable.