operator-keyword

I read about python following PEMDAS that is precedence of multiply is more than division. I ran the following script print 6*2/1*2 Thus python should interpret this like 12/2 i.e 6 , since precedence of multiplication is more than division. But, the answer is 24. Could anyone let me know where the problem is? Thanks! * has the same operator precedence as / . Operators in the same group evaluate left to right, so your expression evaluates as: 6*2 = 12 / 1 = 12 * 2 = 24 Order of precedence in Python P E M D Left to right A S Left to right 来源： https://stackoverflow.com/questions/35845566

Is there an easy way to define an operator alias for the = operator in PostgreSQL? How is that solved for the != and <> operator? Only the <> operator seems to be in pg_operators. Is the != operator hard-coded? This is needed for an application which uses a self-defined operator. In most environments this operator should act like a = , but there are some cases where we define a special behavior by creating an own operator and operator class. But for the normal case our operator should just be an alias for the = operator, so that it is transparent to the application which implementation is used

For instance, these are defined in the operator module and can be used as such: import operator print operator.__add__ # alias add -> + print operator.__sub__ # alias sub -> - print operator.__and__ # alias and_ -> & print operator.__or__ # alias or_ -> | Then what is the equivalent of and and or ? print operator."and ?????" # should be boolean-and print operator."or ????" # should be boolean-or These do not exist. The best you can do is to replace them with a lambda: band = (lambda x,y: x and y) bor = (lambda x,y: x or y) The reason is you can not implement the complete behavior of and or or

What exactly is the <> operator in Python, and why is it undocumented (as far as I can tell)? Is it the same as != or is not ? In Python 2.x , <> is the same as != (i.e. "not equal to" , rather than is not which is "not identical to" ), but the latter is preferred: The comparison operators <> and != are alternate spellings of the same operator. != is the preferred spelling; <> is obsolescent. In 3.x, <> has been removed and only != exists. It is documented, but you're not supposed to use it. Your guess about it being equivalent to != is correct. Quoting the Python 2 documentation : != can also

If I've overloaded operator+ and operator= do I still need to overload operator+= for something like this to work: MyClass mc1, mc2; mc1 += mc2; operator+= is not a composite of + and =, therefore you do need to overload it explicitly, since compiler do not know to build puzzles for you. but still you do able to benefit from already defined/overloaded operators, by using them inside operator+=. Yes, you need to define that as well. A common trick however, is to define operator+= , and then implement operator+ in terms of it, something like this: MyClass operator+ (MyClass lhs, const MyClass&

I have a question about implementing a shared iterator interface. As common practice for postix operator the function might look like this: IteratorClass operator ++(int) { IteratorClass temp = *this; //increment stuff return temp } And most of the time this is fine. In my case I am trying to implement 3 iterators for one class. Each iterator will load a local collection class with data but each derived iterator would load it in a different way. Because the collection class would be the same and all of the code for the operators( postfix/prefix ++/--, *) would be the same I thought a nice way

In order to use cout as such : std::cout << myObject, why do I have to pass an ostream object? I thought that was an implicit parameter. ostream &operator<<(ostream &out, const myClass &o) { out << o.fname << " " << o.lname; return out; } Thanks You aren't adding another member function to ostream , since that would require redefining the class. You can't add it to myClass , since the ostream goes first. The only thing you can do is add an overload to an independent function, which is what you're doing in the example. Only if it is a member function of the class that would otherwise be the