Getting a total from a user defined variable

[Salih Dincer]

On Friday, 21 April 2023 at 05:23:14 UTC, Joel wrote:
>
> Or: p.map!"a.age".sum; works too.

If it was me I would use each().  But D is such a powerful 
language that you have many alternatives:

```d
import std.algorithm, std.range, std.stdio;

struct Person { string name; int age; }
auto totalPersonAge = (int result, Person person)
                         => result + person.age;
void main()
{
     auto p = [
          Person("Kocaeli", 41),
          Person("Konya", 42)
     ];

     p.map!(a => a.age).reduce!"a + b".writeln;
     p.map!"a.age".reduce!"a + b".writeln;

     auto result = reduce!((a, b) => a + b.age)(0, p);
     result.writeln;

     assert(result == reduce!totalPersonAge(0, p));
     assert(result == p.fold!totalPersonAge(0));
     assert(p.map!(a => a.age).sum == p.map!"a.age".sum);


     size_t total;
     p.each!( (ref person) => total += person.age);
     total.writeln;
}
```
SDB at 79