Sunday, March 28, 2010

A new language

Why, oh why, would I curse the world with another programming language? The answer is my typical, "Why not?". More seriously, there are minor deficiencies that I would like to address in the modern mainstream languages. The language I will design will be an incremental improvement over what we currently have. I don't expect it to gain much traction, but it should be enjoyable to program in and it will make for a nice side project.

Here are the major things I wish to have in my language
1. Type inferencing
2. Mutable/Immutable variables - you should be able to specify if a variable is mutable or immutable. By default, local variables are mutable. Non local variables (member variables and static variables) are by default immutable.
3. Non-nullable types - By default all types are non-nullable. You can wrap the type in a Nullable<T> and use the Nullable<T>.Null object to represent null.
4. Generic types - types can be generic.
5. "Duck" interfaces - types can be cast to an interface that they don't implement so long as they implement the correct functions. It must be an explicit cast (unless the interface is unnamed), but the cast will succeed.
6. Unnamed interfaces - When defining a generic function, you can specify an interface that the parameter must implement. The incoming object will be implicitly cast to this unnamed interface.
For example:
int f<T implements { void foo(); }>(T incoming)
7. immutable methods - methods are, by default, immutable. They can not change any of the mutable or immutable members. A method may be specified as mutable, but mutable methods may not be called on immutable objects.
8. Metaprogramming support - Compile time support for metaprogramming should come from a few different sources. First, a standard AST will be provided that can be manipulated through annotation. Basically, an annotation is like a macro that takes a statement and transforms the AST into a different statement. For example, you could write a "memoize" functional annotation that accepts a function declaration and replaces it with a different declaration that is memoized. In addition, metaprogramming can come through compiler event hooks such as "onInheritance", "onCast", "onDeclaration", etc...
9. Unit test support - I'm not yet sure what this will end up looking like, but I do plan on having the ability to write short, inline unit tests at the point of method declaration. It will act as both a user guide as well as a documented test.
10. No "new" keyword - I have never understood the point of the "new" keyword in Java and C#. Therefore, it is gone.
11. No more try - I really hate the try/catch thing. In The Design and Evolution of C++, Bjarne writes about how he had a version without try, but it was confusing. I think it is time to resurrect his experiments. I'm not yet sure of the final form, but I'm sure it will be tryless.
12. Inheritance is deprecated - Other than interfacing with other languages, there should be no need or desire for inheritance. Much of what it was designed to accomplish can be done better through syntax macros and composition. Inheritance will be kept for compatibility with Java/C#/etc..., but its use in native libraries will be deprecated.

Ok, that's 12 things that I see for my language. I don't have a name for it yet, but will accept any suggestions :) I plan to target the .net runtime at first, but the JVM should be a target as well. Comments are welcome.

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