Generics, another type of metaprogramming

This is probably obvious for most of you, but since I didn’t realize it until now, I will bring it to your attention. This C++ tutorial about templates http://www.cplusplus.com/doc/tutorial/templates.html points out that templates is compiled on demand. Close to the end of the article it states;

“From the point of view of the compiler, templates are not normal functions or classes. They are compiled on demand, meaning that the code of a template function is not compiled until an instantiation with specific template arguments is required. At that moment, when an instantiation is required, the compiler generates a function specifically for those arguments from the template.”

So what you do when you build templates in C++ is utilizing the metaprogramming paradigm in compile time. Now, referring to one of my earlier posts called Metaprogramming, I quote Wikipedia who states;

“Not all metaprogramming involves generative programming. If programs are modifiable at runtime (such as in Lisp, Python, Smalltalk, Ruby, PHP, Perl, and Tcl), then techniques can be used to perform metaprogramming without actually generating source code.”

I realize that the languages spoken of in the Wikipedia may perform other types of runtime metaprogramming, also any or none of these languages may or may not utilize generics. However looking at this text, I figure that metaprogramming is clearly a component in generics, even if it is done in runtime or compile time. One could argue that the programmer should be able to choose if a certain implementation of generics should be evaluated in compile time or runtime.

Finally, would it not be possible to define the functionality of generics if the possibility of generic metaprogramming, compile time or runtime, is available in the given language? If so, would you regard generics as a programming pattern rather than a programming paradigm? Are there more programming paradigms that we could squeeze under the roof of metaprogramming?

PS: I should bring my selfe to compile a generics example in C# and take a look at the resulting IL.

What will the others think?

So in my last post I lightly shared some of my philosophical thoughts about generics. I can't say that I really understand what I’m on about in that post. However there is a lot of stuff that could be done to the most common languages out there. What I like about C#, is the fact that Microsoft continue to develop the language. This encourage the thought that we might have a really good programming language some day.

All of this is interesting, and I am always interested in ways to better my code. New syntax gives me more power and possibly new ways to design and write better code. So I am a coding geek, but I am also a professional. S0 when someone tells me that functional programming will improve my code and make it easier to maintain, then I can agree with that person to a certain level. Now, some of you might think that I am stupid to agree to this only “to a certain level”, but most programmers isn't interested in experimenting with new syntax that they feel uncomfortable with. And they usualy state that the way they've always solved problems work, changing it will only introduce more risk then reducing.

So what will happen when we enter the full blown era of C# 3? Well I will of course take advantage of this in my design. And I will probably write the toughest parts in our projects myself, but what will happen when one of the other programmers must put a lambda expression into a method call that I have written? I think they will question my thinking. It doesn’t matter what I think, they are content with how they solve problems already.

Let’s face it, functional programming and full blown utilization of generics turn object oriented programming on the edge. It’s totally a new way of thinking. And I don’t think that many programmers out there are ready for it, or even interested in getting ready for it.

My final point is that when I act system architect, I also have the competence of my collegues in mind. Not doing so will risk the time frame of the project. But keep in mind that I also have their personal education to think about. There must be balance.

Generics C# 2.0

I'm not an experienced programmer when it comes to generics. I thought that I was. However, the more interested I get in programming languages, the more I tend to look at other languages. Now I realize C# 2 is limited.

Disclaimer: Understand that I limit my discussion to C# 2 as reference, I haven’t checked out C# 3 fully just yet, so I will not even bother stating anything about it. Also realize that this particular subject isn't my primary. Johan (blog in Swedish http://hoomla.blogspot.com/), a friend of mine introduced me to the mysterious world of questioning why languages look the way they look. I find myself thinking in other patterns now days, that’s all. So I have some thoughts that I want to put down.

You all know how List<> work, you declare your List<> and give it a type to adopt. Then we have Dictionary<,> where you define two types that you want the class to adopt. Both are good, you can do great stuff with these things. But what if you could declare something like an Array<Tn> where n is a variable number of T’s. Example, I want an Array that holds two strings and a integer, then I would do this Array<string, string, int>. Or if I wanted an Array with one string, one integer and MyType, then I would declare it Array<string, int, MyType>.

As far as I understand, some languages have support for this, it’s called Tuples. F# has Tuples, I haven’t investigated if it is what I think it is just yet. So how would we go about using this generic generics then? What would a foreach look like? I don’t know, could we use foreach or should we need to use more functional programming?

However, generics aren’t limited to arrays or lists. That’s just the most obvious reason to use them. FPSharp is a great example of what you can do with generics (http://sourceforge.net/projects/fpsharp). Credit goes to Johan who find and investigate tons of these things every day.