foreach loop

[wobbles via Digitalmars-d-learn]

On Tuesday, 3 November 2015 at 15:06:00 UTC, Namal wrote:
> On Tuesday, 3 November 2015 at 14:52:19 UTC, Adam D. Ruppe 
> wrote:
>> On Tuesday, 3 November 2015 at 14:47:14 UTC, Namal wrote:
>>> I remember it is possible to get the index for each element 
>>> in the foreach loop, but I forgot how to do it. Can you help 
>>> me out please. Thx.
>>
>> for many of them it is as simple as:
>>
>> foreach(index, element; array) { }
>
> Thank you. I am still struggling with the functional ways of D. 
> Now how could I write this foreach loop the functional way?
>
> bool[] arr = [ture, false, ture, ...];
>
> int count;
> foreach(i;arr){
>
>   if(!i)
>     count++;
> }
> writeln(count);

writefln("Count is: %s", arr
   .filter!(a => a==true)
   .sum);

// Note: std.algorithm.sum is the same as
// std.algorithm.reduce!((a,b)=a+b);