This is not entirely a D question, but I'm not sure what about my mergesort implementation went wrong.

T[] merge(T)(T[] arr1, T[] arr2) {
    T[] result;
    result.reserve(arr1.length + arr2.length);

    ulong arr1_idx = 0, arr2_idx = 0;
    while (arr1_idx < arr1.length && arr2_idx < arr2.length)
        result ~= arr1[arr1_idx] < arr2[arr2_idx] ? arr1[arr1_idx++] : arr2[arr2_idx++];
    return result;
}

T[] sort(T)(T[] arr) {
    return arr.length < 2 ? arr : merge(sort(arr[0 .. $ / 2]), sort(arr[$ / 2 .. $]));
}

Given an array, it just returns a 1 length array. What's causing this?

On Sunday, 29 December 2019 at 11:02:34 UTC, Adnan wrote:
>     while (arr1_idx < arr1.length && arr2_idx < arr2.length)
>         result ~= arr1[arr1_idx] < arr2[arr2_idx] ? arr1[arr1_idx++] : arr2[arr2_idx++];
>
> Given an array, it just returns a 1 length array. What's causing this?

This loop stops as soon as arr1 _or_ arr2 are exhausted. Then, merge() will wrongly discard the remainder of the array that is not yet exhausted.

The templating is good!

-- Simon