Menu
Search

Forums

Forum Index

Thread overview
Getting a total from a user defined variable
Apr 20, 2023
Joel
Apr 20, 2023
John Chapman
Apr 21, 2023
Joel
Apr 21, 2023
Salih Dincer
Apr 20, 2023
Ferhat Kurtulmuş
April 20, 2023
Gravatar of JoelPosted by JoelReply
Joel
Gravatar of Joel


Reply
import std;

struct Person {
    string name;
    ulong age;
}

void main() {
    auto p=[Person("Joel", 43), Person("Timothy", 40)];
    writeln("Total: ", p.reduce!((a,b) => a.age+b.age)(0UL)); // how do I get the total of ages added together?
}
April 20, 2023
Gravatar of John ChapmanPosted by John Chapman
in reply to Joel		Reply
John Chapman
Gravatar of John Chapman
Posted in reply to Joel


Reply

On Thursday, 20 April 2023 at 19:41:21 UTC, Joel wrote:

>

// how do I get the total of ages added together?

p.map!(x => x.age).sum();

April 20, 2023
Gravatar of Ferhat KurtulmuşPosted by Ferhat Kurtulmuş
in reply to Joel		Reply
Ferhat Kurtulmuş
Gravatar of Ferhat Kurtulmuş
Posted in reply to Joel


Reply

On Thursday, 20 April 2023 at 19:41:21 UTC, Joel wrote:

> 
import std;

struct Person {
    string name;
    ulong age;
}

void main() {
    auto p=[Person("Joel", 43), Person("Timothy", 40)];
    writeln("Total: ", p.reduce!((a,b) => a.age+b.age)(0UL)); // how do I get the total of ages added together?
}

import std;

struct Person {
    string name;
    ulong age;
}

void main() {
    auto p=[Person("Joel", 43), Person("Timothy", 40)];

    writeln("Total: ", p.map!(a => a.age).reduce!"a + b");
}
April 20, 2023
Gravatar of Steven SchveighofferPosted by Steven Schveighoffer
in reply to Joel		Reply
Steven Schveighoffer
Gravatar of Steven Schveighoffer
Posted in reply to Joel


Reply
```d
writeln("Total: ", p.fold!((a,b) => a+b.age)(0UL));
// or
writeln("Total: ", reduce!((a,b) => a+b.age)(0UL, p));
```

Note that `reduce` is the old version of `fold`, which happened when UFCS became a thing.

-Steve
April 21, 2023
Gravatar of JoelPosted by Joel
in reply to John Chapman		Reply
Joel
Gravatar of Joel
Posted in reply to John Chapman


Reply

On Thursday, 20 April 2023 at 21:28:48 UTC, John Chapman wrote:

>

On Thursday, 20 April 2023 at 19:41:21 UTC, Joel wrote:

>

// how do I get the total of ages added together?

p.map!(x => x.age).sum();

Or: p.map!"a.age".sum; works too.

April 21, 2023
Gravatar of Salih DincerPosted by Salih Dincer
in reply to Joel		Reply
Salih Dincer
Gravatar of Salih Dincer
Posted in reply to Joel


Reply

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:

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@79