import std.stdio:writeln;

ref int func(return ref int a){
    a = 6; // modifies a as expected
    return a;
}
void main(){
    int a = 5;
    auto c = func(a); // I expected c to alias a here
    c = 10; // Expected to modify a as well
    writeln(a); // prints 6 :(
}

The spec states:

Then why does the reference to a not get returned ?

On Wednesday, 5 January 2022 at 04:35:12 UTC, Tejas wrote:

import std.stdio:writeln;

ref int func(return ref int a){
    a = 6; // modifies a as expected
    return a;
}
void main(){
    int a = 5;
    auto c = func(a); // I expected c to alias a here
    c = 10; // Expected to modify a as well
    writeln(a); // prints 6 :(
}

Local variables cannot be references, so when you assign the reference returned from func to the variable auto c, a copy is created.

To make this work the way you want it to, you must use a pointer:

int a = 5;
auto p = &func(a); // use & to get a pointer
*p = 10;
writeln(a); // prints 10

On Wednesday, 5 January 2022 at 04:35:12 UTC, Tejas wrote:

import std.stdio:writeln;

ref int func(return ref int a){
    a = 6; // modifies a as expected
    return a;
}
void main(){
    int a = 5;
    auto c = func(a); // I expected c to alias a here
    c = 10; // Expected to modify a as well
    writeln(a); // prints 6 :(
}

It is returned. But initializing c with it makes a copy. This will mutate a:

func(a) = 10;

On Wednesday, 5 January 2022 at 05:15:30 UTC, Paul Backus wrote:

import std.stdio:writeln;

ref int func(return ref int a){
    a = 6; // modifies a as expected
    return a;
}
void main(){
    int a = 5;
    auto c = func(a); // I expected c to alias a here
    c = 10; // Expected to modify a as well
    writeln(a); // prints 6 :(
}

int a = 5;
auto p = &func(a); // use & to get a pointer
*p = 10;
writeln(a); // prints 10

The entire reason I wanted to get a ref was so that I can avoid the * :(
Didn't know you could take the address of a function invocation though, so asking this wasn't completely redundant

Thank you :D

Guess I'll be stuck with ol' struct Ref(T){...}

On Wednesday, 5 January 2022 at 05:17:10 UTC, Stanislav Blinov wrote:

Oh...
Wish we had real ref ;(

func(a) = 10;

Thank you for your help!

On Wednesday, 5 January 2022 at 05:38:45 UTC, Tejas wrote:

I don't know what the real code behind the reduced example is, but maybe you can structure your code such that the subsequent modification c = 10 happens in its own function. Then you can pass the result of func(a) to that function by ref.

On Wednesday, 5 January 2022 at 08:58:44 UTC, Dennis wrote:

There isn't any complex code behind this.

I was simply trying to emulate C++'s int&(or T& in general)