Delphi Unleashed Чарльза Калверта from
http://www.youtube.com/watch?v=V1vQf4qyMXgEffective Java - Still Effective After All These Years
B честнее С, С честнее Java, очевидно же не про транзитивность
from
http://cm.bell-labs.com/cm/cs/who/dmr/kbman.html :
3.0 values and Lvalues
An rvalue is a binary bit pattern of a fixed length. On the PDP-11 it is 16 bits. Objects are rvalues of different kinds such as integers, labels, vectors and functions. The actual kind of object represented is called the type of the rvalue.
A B expression can be evaluated to yield an rvalue, but its type is undefined until the rvalue is used in some context. It is then assumed to represent an object of the required type. For example, in the following function call
(b? f:g[i] )(1, x>1)
The expression (b?f:g[i]) is evaluated to yield an rvalue which is interpreted to be of type function. Whether f and g[i] are in fact functions is not checked. Similarly, b is assumed to be of type truth value, x to be type integer etc.
There is no check to insure that here are no type mismatches. Similarly, there are no wanted, or unwanted, type conversions.
An lvalue is a bit pattern representing a storage location containing an rvalue. An lvalue is a type in B. The unary operator * can be used to interpret an rvalue as an lvalue. Thus
*X
evaluates the expression x to yield an rvalue, which is then interpreted as an lvalue. If it is then used in an rvalue context, the application of * yields the rvalue therein stored. The operator * can be thought of as indirection.
The unary operator & can be used to interpret an lvalue as an rvalue. Thus
&x
evaluates the expression x as an lvalue. The application of & then yields the lvalue as an rvalue. The operator & can therefore be thought of as the address function.
The names lvalue and rvalue come from the assignment statement which requires an lvalue on the left and an rvalue on the right.