[BEGINNER] reccurence! and sequence!

[helxi via Digitalmars-d-learn]

On Thursday, 6 July 2017 at 00:21:44 UTC, Ali Çehreli wrote:
> On 07/05/2017 04:38 PM, helxi wrote:
>
> >> [...]
> >
> > Oh thank you. Just 2 follow-up questions:
> >> [...]
> > 1. In the last example of reccurence, what does n in (a,n)
> refer to?
>
> n is "the index of the current value". Each time the lambda is 
> called,
>
>   a[n] is what is being generated
>   a[n-1] is the previous value
>   a[0] is the same as a[n-1]? (I find this confusing)
>
> > 2. How would you chain until! with reccurence? For example I
> want to
> > compute 1, 10, 100, ..., (until the value remains smaller
> than 1000_000)?
>
> import std.stdio;
> import std.algorithm;
> import std.range;
>
> void main() {
>     auto r = recurrence!((a, n) => a[n-1] * 10)(1);
>     auto u = r.until!(a => a >= 1_000_000);
>     writeln(u);
> }
>
> [1, 10, 100, 1000, 10000, 100000]
>
> Ali

Hmm, I get it now. Thank you very much.