This is the first in a series where I am going to read through the O’Reilly C++ In A Nutshell language reference and blog about each part. This is mainly for me, to make sure I fully understand the language, and for you, if you care.
This first one will be like a few others where I will group a set of pieces into one entry. For instance, this is all of the operators instead of today blogging about ‘and’ and tomorrow blogging about ‘or’. Although, I will call out the cast operators, throw and new/delete into a separate posting
Operators
and
This is the logical and operator, equivalent to &&. And returns true if both sides evaluate to true.
and_eq
equivalent to &= and should more appropriately be named “bitand_eq”. A &= B is equivalent to A = A & B. However, they are two different operators and are overloaded separately, so it is possible for them to have two different meanings.
bitand
bitand, which is the same as &, performs a bitwise and of the two operands. For instance 0x02 & 0x01 == 0x00, because 2 and 1 share no bits in common. Also, 0x02 & 0x03 == 0x02 because the ‘2’ bit is shared.
bitor
bitor, equivalent to |, performs a bitwise or of the two operands. So, 0x02 | 0x03 == 0x03. If a bit is in either operand, it is in the result.
compl
compl, equivalent to ~, performs a bitwise complement of the operand. For instance, ~0x01 == 0xFE (the result has every bit set EXCEPT for the bits in the operand).
not
not, equivalent to !, performs a logical negation. !true == false. It is of note that any non 0 value in C++ resolves to true. Therefor !5 == false !0 == true.
not_eq
not_eq is equivalent to !=. true != false, 5 != 4 both evaluate to true. not_eq is a different operator from !(5 == 4) and could be overloaded separately in a class.
or
or, equivalent to ||, returns true if either operand evalutes to true. For instance (true || false) == true, (false || false) == false.
or_eq
or_eq, which should be named bitor_eq, is equivalent to |= and performs the same operation as A = A | B. Note, like the other *_eq operators, it is technically different from the above example.
sizeof
sizeof returns the number of bytes needed to store an object. For instance sizeof(char[5]) == 5, sizeof(int) = 4 (on most 32bit platforms). It is of note that the size may be larger than you are expecting. Some platforms require padding of data between members of a struct, for instance. Also, classes containing virtual functions are larger than classes not containing virtual functions. Thirdly, it should be representative of the actual data being stored. That is, adding a new non-virtual function should not increase the sizeof(classname), because the function’s code is stored at the class level, not the object.
typeid
Returns a const reference to a type_info object which contains information about the object or type referenced.
xor
xor, equivalent to ^, performs a bitwise exclusive or on the two operands. That is, a bit is only set in the result if it is one operand or the other, but not both. So, 0x02 ^ 0x01 == 0x03. 0x03 ^ 0x01 == 0x02.
xor_eq
Equivalant to ^= which is almost equivalent to A = A ^ B. See other _eq operators above.
