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) { }

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);

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);

On Tuesday, 3 November 2015 at 15:10:43 UTC, wobbles wrote:
> 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:
>>>> [...]
>>>
>>> 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);

Oh, I realise now you were counting the number of 'false' values.
I counted the true values - so the filter line is wrong here.

On Tuesday, 3 November 2015 at 15:10:43 UTC, wobbles wrote:
> 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);

How do I save sum as integer or something I try;

	arr.writeln;
	return arr.filter!(a=>a==false).sum;

but I get
[true, false, true, false, true, true, true, false, true, false]
0

On Tuesday, 3 November 2015 at 15:10:43 UTC, wobbles wrote:
> 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);

well I tried this that way, but my count stays 0, same as if I do it in an int function with a return though I clearly have some false elements in the arr.

On Tuesday, 3 November 2015 at 15:29:31 UTC, Namal wrote:
>> 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);
>

Shouldn't you be using walkLength instead of sum, since you are counting the left over values?

import std.range : walkLength;
writefln("Count is: %s", arr
  .filter!(a => a==false)
  .walkLength);

On Tuesday, 3 November 2015 at 15:42:16 UTC, Edwin van Leeuwen wrote:
> On Tuesday, 3 November 2015 at 15:29:31 UTC, Namal wrote:
>>> 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);
>>
>
> Shouldn't you be using walkLength instead of sum, since you are counting the left over values?
>
> import std.range : walkLength;
> writefln("Count is: %s", arr
>   .filter!(a => a==false)
>   .walkLength);

That would work also yes.
Be interesting to know which is more efficient actually - I suspect they're very similar.

On Tuesday, 3 November 2015 at 16:55:44 UTC, wobbles wrote:
> On Tuesday, 3 November 2015 at 15:42:16 UTC, Edwin van Leeuwen wrote:
>> On Tuesday, 3 November 2015 at 15:29:31 UTC, Namal wrote:
>>>> 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);
>>>
>>
>> Shouldn't you be using walkLength instead of sum, since you are counting the left over values?
>>
>> import std.range : walkLength;
>> writefln("Count is: %s", arr
>>   .filter!(a => a==false)
>>   .walkLength);
>
> That would work also yes.
> Be interesting to know which is more efficient actually - I suspect they're very similar.

false converts to zero, so
[false,false,false].sum == 0

Of course true converts to one ->
[true,true,true].sum == 3

On Tuesday, 3 November 2015 at 15:29:31 UTC, Namal wrote:
> well I tried this that way, but my count stays 0, same as if I do it in an int function with a return though I clearly have some false elements in the arr.

You could also use count: http://dlang.org/phobos/std_algorithm_searching.html#count

return arr.count!(x => !x);