D versus Objective C Comparison

[Michel Fortin]

On 2009-02-02 01:39:40 -0500, John Reimer <terminal.node at gmail.com> said:

> "The Objective-C language defers as much as it can from compile time 
> and link time to runtime.  Whenever possible, it does things 
> dynamically.  This means that the language requires not just a 
> compiler, but also a runtime system to execute the compiled code.  The 
> runtime system acts as a kind of operating system for the Objective-C 
> language; it's what makes the language work."
> 
> This is actually kind of interesting because it would seem to make 
> Objective-C slightly comparable to the C# language in that it's more 
> than just a language (as is Java).  It's a platform (and the beauty of 
> the platform is really only extensively demonstrated by the OS runtime 
> functionality that supports it ... and Cocoa).

Yeah, but the Objective-C runtime is pretty microscopic compared to 
Java or the C# runtime. There is no such thing as a virtual machine. 
What the Objecitve-C runtime does is this, and only this:

1. It manages a list of registered classes, and their associated methods.
2. It provides a method dispatch mechanism, and manages a list of 
registered selectors.
3. It provides various support routines for the compiler (exception 
handling, synchronization).

For comparison, the D runtime does half of 1, and whole of 3, and a lot 
more. If you start counting parts of the Foundation framework in the 
runtime, then you'd have a base object class, an exception class, a 
thread class... But technically, Foundation is not part of the runtime, 
even if it's pretty necessary to do anything.

I'd say that the Objective-C runtime is smaller than druntime since it 
does less (no TypeInfo, no array concat, no associative array, no 
thread support, etc.), although I haven't measured anything. On the 
other hand, the "standard library" (the Foundation framework) is 
probably bigger than both Phobos and Tango together.

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/