Re: Infinite fibonacci sequence, lazy take first 42 values

[Alain De Vos via Digitalmars-d-learn]

On Thursday, 21 April 2022 at 04:36:13 UTC, Salih Dincer wrote:
On Thursday, 21 April 2022 at 03:41:24 UTC, Ali Çehreli wrote:
On 4/20/22 19:11, Alain De Vos wrote:
> Maybe there are multiple solutions ?

Indeed. :)

I have a Range struct here:

  
http://ddili.org/ders/d.en/ranges.html#ix_ranges.infinite%20range


My favorite is the struct range.  Because it is more 
understandable and personalized.  Moreover, you can limit it 
without using ```take()```.

```d
struct FibonacciRange(int l)
{
  long a = 1, b = 1;

  bool empty()
  {
    return a > l;
  }

  long front() const
  {
   return a;
  }

  void popFront()
  {
    auto t = a;
    a = b;
    b += t;
  }
}

enum limit = 16;

void main()
{
  import std.stdio;
  FibonacciRange!limit fibs;
  fibs.write(": ");

  import std.algorithm;
  auto total = fibs.sum;
  total.writeln;

  assert(total == 33);
}
```
SDB@79

This example limits the maximum value returned by the fibonacci 
function. f(n) < limit
But it does not allow to return the n-th element of a fibonacci 
function.