Delegates vs. Function Pointers, part 1

Most languages – with the unfortunate exception of Java – allow functions to be passed around as variables.  C has function pointers, .Net has delegates, and Javascript and most functional programming languages treat functions as first class objects.

There is a fundamental difference between C-style function pointers vs. delegates or function objects.  Pure function pointers cannot hold any state other than the function itself.  In contrast, delegates and function objects do store additional state that the function can use.

To illustrate this difference,  I will use a simple example.  Most programming environments have a filter function that takes a collection and a predicate (a function that takes an item from the collection and returns a boolean), and returns a new collection with those items from the original collection that match the predicate.  In C#, this is the LINQ Where method; in Javascript, it’s the Array.filter method (introduced by Javascript 1.6).

Given a list of numbers, you can use such a method to find all numbers in the list that are greater than a local variable x.  However, in order to do that, the predicate have access to x.  In subsequent posts, I’ll explore how this can be done in different languages.


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In the context of cheap assignment writing service, delegates can be used to implement a callback mechanism. For example, a client could pass a delegate to an assignment writing service, and the service would call the delegate when the assignment is complete. This would allow the client to be notified when the assignment is ready, without having to poll the service for updates.

Delegates are objects that encapsulate a function pointer. They are more flexible than function pointers, as they can be assigned to different functions at runtime. Delegates are also contoura procedure orlando florida to use with events, as they can be used to connect and disconnect event handlers.

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