keyword

Today I learnt about the is keyword in Python and tried the following: >>> x=2+2 >>> y=4 >>> x is y True I started off trying is with integers because I knew the answer would be False -- so I found the result very surprising! To give some context, my background is C++ and C# where there is a distinction between value types and object types. In Python, as I now realize, everything is a reference type. It seems the reason that x is y is True is the same as explained in this question, How is the 'is' keyword implemented in Python? , which relates to using is with strings. I.e. the run-time

This question already has an answer here: How to emulate C# as-operator in Java 6 answers As we know C# provides an AS keyword which automatically performs a check whether the Object is of a type and if it is, it then casts it to the needed type else gives a null. public class User { } .... Object obj = someObj; User user = obj As User; ... Here in the above example, An Object obj can be of type User or some other type. The user will either get an object of type User or a null. This is because the As keyword of C# first performs a check and if possible then performs a casting of the object to

In python there is a pass keyword for defining an empty function, condition, loop, ... Is there something similar for Ruby? Python Example: def some_function(): # do nothing pass No, there is no such thing in Ruby. If you want an empty block, method, module, class etc., just write an empty block: def some_method end That's it. In Python, every block is required to contain at least one statement, that's why you need a "fake" no-op statement. Ruby doesn't have statements, it only has expressions, and it is perfectly legal for a block to contain zero expressions. nil is probably the equivalent of

What's the meaning of the frozen keyword in Cassandra? I'm trying to read this documentation page: Using a user-defined type , but their explanation for the frozen keyword (which they use in their examples) is not clear enough for me: To support future capabilities, a column definition of a user-defined or tuple type requires the frozen keyword. Cassandra serializes a frozen value having multiple components into a single value. For examples and usage information, see "Using a user-defined type", "Tuple type", and Collection type. I haven't found any other definition or a clear explanation for