D Recurrences

[Ben Grabham]

On 09/06/11 17:57, bearophile wrote:
> Ben Grabham:
>
>> import std.range;
>> import std.stdio;
>> int main() {
>> 	auto a = recurrence!("a[n-1] + a[n-2]")(0,1);
>> 	int i = 0;
>> 	foreach(int n; a) {
>> 		if(i++>  20) break;
>> 		writefln("%d", n);
>> 	}
>> 	return 0;
>> }
>
> This program does something similar to yours (but it doesn't print newlines):
>
>
> import std.stdio, std.range;
>
> void main() {
>      auto fib = recurrence!q{ a[n-1] + a[n-2] }(0, 1);
>      writeln(take(fib, 21));
> }
>
> Bye,
> bearophile

Yeah, thanks

I just wanted to post a bit of code which went wrong :P
Didn't look for optimisations.

Also, how come recurrence isn't properly lazy?
If I define a recurrence and iterate over it twice with foreach, it 
takes the same amount of time due to the stack size being set. Is there 
a way of defining a lazy list that stores the results when calculated?

Thanks,
Nebster