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In all versions of Python, boolean operators treat zero values or empty values such as "", 0, None, 0.0, [], and {} as false, while in general treating non-empty, non-zero values as true. The boolean values True and False were added to the language in Python 2.2.1 as constants (subclassed from 1 and 0 ) and were changed to be full blown ...
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.
The list type is an additive monad, with nil as the monadic zero and append as monadic sum. Lists form a monoid under the append operation. The identity element of the monoid is the empty list, nil. In fact, this is the free monoid over the set of list elements.
In Python, == compares by value. Python's is operator may be used to compare object identities (comparison by reference), and comparisons may be chained—for example, a <= b <= c. Python uses and, or, and not as Boolean operators. Python has a type of expression named a list comprehension, and a more general expression named a generator ...
In other languages, variables are often initialized to known values when created. Examples include: VHDL initializes all standard variables into special 'U' value. It is used in simulation, for debugging, to let the user to know when the don't care initial values, through the multi-valued logic, affect the output.
Class variable – Variable defined in a class whose objects all possess the same copy; Instance variable – Member variable of a class that all its objects possess a copy of; List of object-oriented programming languages; Trait (computer programming) – Set of methods that extend the functionality of a class
Even if the variable to capture is non-final, it can always be copied to a temporary final variable just before the class. Capturing of variables by reference can be emulated by using a final reference to a mutable container, for example, a one-element array. The local class will not be able to change the value of the container reference, but ...
The Ada programming language has native support for type invariants (as well as pre- and postconditions, subtype predicates, etc.). A type invariant may be given on a private type (for example to define a relationship between its abstract properties), or on its full definition (typically to help in verifying the correctness of the implementation of the type). [5]