Recursive typedef

[BCS]

Markus Dangl wrote:
> BCS schrieb:
> 
>> But it does make for a cool state machine!!!
>>
>> State at = &seed;
>> while(null !is at) at = cast(State)at();
>>
>> or
>>
>> state at = &seed;
>> while(null !is at.use) at = cast(state)at.use();
> 
> 
> That's exactly what i use it for - it's almost functional programming :)

One interesting things about the delegate form is that it can be used to 
make an *infinite* state machine.


struct state
{
	state delegate(Stream) next;
}

struct nest
{
	nest* root;

	state scan(Stream ins)
	{
		nest* tmp;
		state ret;

		if(ins.eof && root !is null)
			throw new Error("invalid");

		switch(ins.getc)
		{
			case '{':
				tmp = new nest;
				tmp.root = this;
				ret.next = &tmp.scan;
				return ret;
			
			case '}':
				if(root is null)
					throw new Error("invalid");
				ret.next = &root.scan;
				return ret;
			
			default:
				ret.next = &this.scan;
				return ret;				
		}
	}
}