2011/10/20 Florian Klämpfl <flor...@freepascal.org> > If anybody does not see why increasing complexity without a good reason > should be avoided, I recommend: > > http://www.youtube.com/watch?v=kYUrqdUyEpI >
:-) There is lots of confusion about anonymous functions. The name is misleading, they are called closures in other languages. There was a similar discussion earlier, see : http://www.hu.freepascal.org/lists/fpc-pascal/2010-January/023755.html The origin is from functional languages but it is fine to borrow it to OP, the same way classes and object features were borrowed earlier from other languages. Besides I think the closure addition is almost as important. They have some very important uses, like making multithreading easier. I copy text from Delphi help page again here because it looks so cool: --------------------------------------------------------- Using Code for a Parameter Anonymous methods make it easier to write functions and structures parameterized by code, not just values. Multithreading is a good application for anonymous methods. if you want to execute some code in parallel, you might have a parallel-for function that looks like this: type TProcOfInteger = reference to procedure(x: Integer); procedure ParallelFor(start, finish: Integer; proc: TProcOfInteger); The ParallelFor procedure iterates a procedure over different threads. Assuming this procedure is implemented correctly and efficiently using threads or a thread pool, it could then be easily used to take advantage of multiple processors: procedure CalculateExpensiveThings; var results: array of Integer; begin SetLength(results, 100); ParallelFor(Low(results), High(results), procedure(i: Integer) // \ begin // \ code block results[i] := ExpensiveCalculation(i); // / used as parameter end // / ); // use results end; Contrast this to how it would need to be done without anonymous methods: probably a "task" class with a virtual abstract method, with a concrete descendant for ExpensiveCalculation, and then adding all the tasks to a queue--not nearly as natural or integrated. Here, the "parallel-for" algorithm is the abstraction that is being parameterized by code. In the past, a common way to implement this pattern is with a virtual base class with one or more abstract methods; consider the TThread class and its abstract Execute method. However, anonymous methods make this pattern--parameterizing of algorithms and data structures using code--far easier. Regards, Juha Manninen
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