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The value of %phone-book{'John Doe'} is '555-1212'. The list of keys and values can be extracted using the built-in functions keys and values, respectively. So, for example, to print all the keys of a hash:
Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
In Perl, a return value or values of a subroutine can depend on the context in which it was called. The most fundamental distinction is a scalar context where the calling code expects one value, a list context where the calling code expects a list of values and a void context where the calling code doesn't expect any return value at all.
In computer programming, foreach loop (or for-each loop) is a control flow statement for traversing items in a collection. foreach is usually used in place of a standard for loop statement.
Whether it is a console or a graphical interface application, the program must have an entry point of some sort. The entry point of a C# application is the Main method. There can only be one declaration of this method, and it is a static method in a class. It usually returns void and is passed command-line arguments as an array of strings.
Folds can be regarded as consistently replacing the structural components of a data structure with functions and values. Lists, for example, are built up in many functional languages from two primitives: any list is either an empty list, commonly called nil ([]), or is constructed by prefixing an element in front of another list, creating what is called a cons node ( Cons(X1,Cons(X2,Cons ...
In computer programming, an iterator is an object that progressively provides access to each item of a collection, in order. [1] [2] [3]A collection may provide multiple iterators via its interface that provide items in different orders, such as forwards and backwards.
This feature was eventually removed, and now this in C++ is an r-value. [9] Early versions of C++ did not include references and it has been suggested that had they been so in C++ from the beginning, this would have been a reference, not a pointer. [10] C++ lets objects destroy themselves with the source code statement: delete this.