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digitalmars.D.learn - Range handling difficulties

reply Menjanahary R. R. <megnany afaky.com> writes:
I tried to solve Project Euler [problem 
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.
Apr 24
parent reply "H. S. Teoh" <hsteoh qfbox.info> writes:
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
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

-- 
The trouble with TCP jokes is that it's like hearing the same joke over and
over.
Apr 24
parent Menjanahary R. R. <megnany afaky.com> writes:
On Wednesday, 24 April 2024 at 14:22:10 UTC, H. S. Teoh wrote:

 On Wed, Apr 24, 2024 at 08:08:06AM +0000, Menjanahary R. R. via 
 Digitalmars-d-learn wrote:

 [...]


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


 T


Thanks a lot! You've made my day 😀
Apr 24