Range handling difficulties

[H. S. Teoh]

On Wed, Apr 24, 2024 at 08:08:06AM +0000, Menjanahary R. R. via Digitalmars-d-learn wrote:
> I tried to solve Project Euler [problem
> #2](https://projecteuler.net/problem=2) using
> [Recurrence/recurrence](https://dlang.org/library/std/range/recurrence.html).
> 
> Assuming `genEvenFibonacci` is the appropriate funtion in Explicit
> form, I got what I need like so:
> 
> ```
>     auto evenfib = recurrence!genEvenFibonacci(2uL, 8uL);
> 
>     writeln;
>     evenfib.take(11).sum.writeln;
> ```
> 
> But that's like cheating because there is no prior knowledge of `11`.
> 
> I just got it manually by peeking at the sequence `[2, 8, 34, 144,
> 610, 2584, 10946, 46368, 196418, 832040, 3524578, 14930352]`.
> 
> `14930352` must be filtered out because beyond the limit set!
> 
> How to fix that properly using all the standard library capabilities
> programatically?
> 
> I'm thinking of Range and/or std.algorithm.

	evenfib.until!(n => n > 4_000_000).sum.writeln;


T

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