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POCould the CLR support a "function pointer" value type?
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copied!<p>A few days ago I asked <a href="https://stackoverflow.com/questions/7905962/why-are-delegates-reference-types">why delegates are reference types</a>, based on my misguided notion that all you need for a delegate are two references: one to an object, and one to a function. What I completely overlooked (not because I wasn't aware, simply because I forgot) is that in .NET, delegates are at least <em>partially</em> in place to support events as a built-in implementation of the <a href="http://en.wikipedia.org/wiki/Observer_pattern" rel="nofollow noreferrer">Observer pattern</a>, which means that every delegate supports multiple subscribers by way of an <em>invocation list</em>.</p> <p>This got me thinking, delegates really play two different roles in the .NET world. One is that of a humble function pointer, such as:</p> <pre><code>Action<string> writeLine = Console.WriteLine; </code></pre> <p>The <em>other</em> is that of an observable:</p> <pre><code>textBox.TextChanged += HandleTextChanged; </code></pre> <p>The existence of an invocation list seems to be exclusively for the second role, as in cases like the simple <code>writeLine</code> example above you generally don't even <em>think</em> about subscribers.</p> <p>So really, it seems to me there <em>could</em> be two different "kinds" of delegates: the "function pointer" kind, and the "observable" kind. The former, it seems to me, could be a value type.</p> <p>Now, I'm not arguing that this <em>should</em> be the case, if it's even possible. I am sure there would be a lot of downsides to making this distinction between regular and multicast delegates, such as the likely high frequency of boxing if delegates were value types, the possible need to introduce a new keyword (<code>multicast</code>?), the inevitable developer confusion, etc. What I'm really curious to know is simply if it <em>would</em> be possible, from a CLR perspective, to have a value type that could act as a function pointer.</p> <p>I guess another way of asking this would be: is <code>System.Delegate</code>, with its invocation list and all, basically a fundamental CLR type; or is it a wrapper around a simpler "function reference" type that simply isn't exposed by any CLR languages?</p> <p>I apologize for all of the informal terms I've used that may have confused some of the more educated developers out there.</p>

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