I tried to copy an array into another without affecting in the original array when I try to change the value of any element of the new array, but I failed except with this way in the next code:

'''D
int[] x=[1,2,3];
    int[] y=x.filter!("a==a").array;

    y[1]=800;

    x.writeln;
    y.writeln;
'''

On Tuesday, 9 August 2022 at 18:33:04 UTC, pascal111 wrote:
> I tried to copy an array into another without affecting in the original array when I try to change the value of any element of the new array, but I failed except with this way in the next code:
>
> '''D
> int[] x=[1,2,3];
>     int[] y=x.filter!("a==a").array;
>
>     y[1]=800;
>
>     x.writeln;
>     y.writeln;
> '''

A simpler way to do this is to use the array's built-in .dup method [1]:

    int[] x = [1, 2, 3];
    int[] y = x.dup;
    y[1] = 800;

    writeln(x); // [1, 2, 3]
    writeln(y); // [1, 800, 3]

[1] https://dlang.org/spec/arrays.html#array-properties

Edit "Copying an array into another" in the title.

On Tuesday, 9 August 2022 at 18:41:52 UTC, Paul Backus wrote:
> On Tuesday, 9 August 2022 at 18:33:04 UTC, pascal111 wrote:
>> I tried to copy an array into another without affecting in the original array when I try to change the value of any element of the new array, but I failed except with this way in the next code:
>>
>> '''D
>> int[] x=[1,2,3];
>>     int[] y=x.filter!("a==a").array;
>>
>>     y[1]=800;
>>
>>     x.writeln;
>>     y.writeln;
>> '''
>
> A simpler way to do this is to use the array's built-in .dup method [1]:
>
>     int[] x = [1, 2, 3];
>     int[] y = x.dup;
>     y[1] = 800;
>
>     writeln(x); // [1, 2, 3]
>     writeln(y); // [1, 800, 3]
>
> [1] https://dlang.org/spec/arrays.html#array-properties

I don't know how I forgot this or why it didn't come to my mind because I already indeed had read about ".dup"?! You are right!