• Charles (5/5) Feb 09 2016 This seems to be true of any range function really... is there a
• cym13 (2/7) Feb 09 2016 x.filter!(x_key => x_key % 2 == 1).sum();
• Charles (6/15) Feb 09 2016 Oh man, I really messed up my example, and did a poor one at that.
• Steven Schveighoffer (14/19) Feb 09 2016 An array is not an indexed range. It only works with foreach by key
• Charles (5/17) Feb 09 2016 Exactly! Thanks!
• =?UTF-8?Q?Ali_=c3=87ehreli?= (12/29) Feb 09 2016 For this specific problem, you can combine drop() and stride() (and even...

Charles <csmith.ku2013 gmail.com> writes:

This seems to be true of any range function really... is there a 
way to access the key within my range?

Example of what I want to do:

auto x = [1,2,3,4,5];
x.filter( x_key % 2 == 1 ).sum(); // sum odd elements in array

cym13 <cpicard openmailbox.org> writes:

On Tuesday, 9 February 2016 at 20:40:44 UTC, Charles wrote:
 This seems to be true of any range function really... is there 
 a way to access the key within my range?

 Example of what I want to do:

 auto x = [1,2,3,4,5];
 x.filter( x_key % 2 == 1 ).sum(); // sum odd elements in array

x.filter!(x_key => x_key % 2 == 1).sum();

Charles <csmith.ku2013 gmail.com> writes:

On Tuesday, 9 February 2016 at 20:44:34 UTC, cym13 wrote:
 On Tuesday, 9 February 2016 at 20:40:44 UTC, Charles wrote:
 This seems to be true of any range function really... is there 
 a way to access the key within my range?

 Example of what I want to do:

 auto x = [1,2,3,4,5];
 x.filter( x_key % 2 == 1 ).sum(); // sum odd elements in array

 x.filter!(x_key => x_key % 2 == 1).sum();

Oh man, I really messed up my example, and did a poor one at that.

Better example:

auto x = [2,4,6,8,10];
x.filter( x_key => x_key % 2 == 1 ).sum(); // sums 2 + 6 + 10 == 
18

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 2/9/16 3:40 PM, Charles wrote:
 This seems to be true of any range function really... is there a way to
 access the key within my range?

 Example of what I want to do:

 auto x = [1,2,3,4,5];
 x.filter( x_key % 2 == 1 ).sum(); // sum odd elements in array

An array is not an indexed range. It only works with foreach by key 
because of special foreach behavior.

What you want is std.range.enumerate:

import std.range;
import std.algorithm;
import std.stdio;

void main()
{
     auto x = [1, 2, 3, 4, 5];
     writeln(x.enumerate.filter!(a => a[0] % 2 == 1).map!(a => 
a[1]).sum); // 6
}

-Steve

Charles <csmith.ku2013 gmail.com> writes:

On Tuesday, 9 February 2016 at 20:48:01 UTC, Steven Schveighoffer 
wrote:
 On 2/9/16 3:40 PM, Charles wrote:
 This seems to be true of any range function really... is there 
 a way to
 access the key within my range?

 Example of what I want to do:

 auto x = [1,2,3,4,5];
 x.filter( x_key % 2 == 1 ).sum(); // sum odd elements in array

 An array is not an indexed range. It only works with foreach by 
 key because of special foreach behavior.

 What you want is std.range.enumerate


Exactly! Thanks!

Interestingly, hackerrank doesn't seem to have it. They're using 
2.067.0-b1 on Ubuntu 14.04.

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 02/09/2016 12:54 PM, Charles wrote:
 On Tuesday, 9 February 2016 at 20:48:01 UTC, Steven Schveighoffer wrote:
 On 2/9/16 3:40 PM, Charles wrote:
 This seems to be true of any range function really... is there a way to
 access the key within my range?

 Example of what I want to do:

 auto x = [1,2,3,4,5];
 x.filter( x_key % 2 == 1 ).sum(); // sum odd elements in array

 An array is not an indexed range. It only works with foreach by key
 because of special foreach behavior.

 What you want is std.range.enumerate


 Exactly! Thanks!

 Interestingly, hackerrank doesn't seem to have it. They're using
 2.067.0-b1 on Ubuntu 14.04.

For this specific problem, you can combine drop() and stride() (and even 
sum()! ;) ):

import std.range;
import std.algorithm;
import std.stdio;

void main()
{
     auto x = [1, 2, 3, 4, 5];
     writeln(x.drop(1).stride(2).sum); // 6
}

Ali