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The foreach statement in some languages has some defined order, processing each item in the collection from the first to the last. The foreach statement in many other languages, especially array programming languages, does not have any particular order.
The foreach statement is derived from the for statement and makes use of a certain pattern described in C#'s language specification in order to obtain and use an enumerator of elements to iterate over. Each item in the given collection will be returned and reachable in the context of the code block.
Array with all the doubles from 1 to 9 inclusive: my @doubles = map { $_ * 2 } 1 .. 9 ; Array with the names of the customers based in Rio de Janeiro (from array of hashes):
As a precursor to the lambda functions introduced in C# 3.0, C#2.0 added anonymous delegates. These provide closure-like functionality to C#. [3] Code inside the body of an anonymous delegate has full read/write access to local variables, method parameters, and class members in scope of the delegate, excepting out and ref parameters. For example:-
The for statement accepts either arrays or Iterable s. All collections implement Iterable. This means that the same short syntax can be used in for-loops. The foreach statement iterates through a sequence using a specific implementation of the GetEnumerator method, usually implemented through the IEnumerable or IEnumerable<T> interface. [38]
However, the foreach statement in C# can operate on any object providing such a method, even if it does not implement IEnumerable (duck typing). [17]: 89 Both interfaces were expanded into generic versions in .NET 2.0. The following shows a simple use of iterators in C# 2.0:
For example, to perform an element by element sum of two arrays, a and b to produce a third c, it is only necessary to write c = a + b In addition to support for vectorized arithmetic and relational operations, these languages also vectorize common mathematical functions such as sine.
Examples of reference types are object (the ultimate base class for all other C# classes), System. String (a string of Unicode characters), and System. Array (a base class for all C# arrays). Both type categories are extensible with user-defined types.