Using constructors with arrays in D

a simple loop should do (and it's the most readable)

foreach(ref el;a){    el=new A(5);}

or you can use the array initializer:

A[] a=[new A(5),new A(5),new A(5),new A(5),new A(5),       new A(5),new A(5),new A(5),new A(5),new A(5)];

If you're dealing with a value type, you can use std.array.replicate.

auto a = replicate([5], 50);

would create an int[] of length 50 where each element is 5. You can do the same with a reference type, but all of the elements are going to refer to the same object.

auto a = replicate([new A(5)], 50);

will only call A's constructor once, and you'll end up with an A[] where all of the elements refer to the same object. If you want them to refer to separate objects, you're either going to have to set each element individually

auto a = new A[](50);foreach(ref e; a)    e = new A(5);

or initialize the whole array with a literal

auto a = [new A(5), new A(5), new A(5)];

But that clearly will only work for relatively small arrays.

If you really want to do it in one line, you could write a macro to do it for you. I've borrowed code for the actual initialisation from the other answers.

template allocate(T) {    T[] allocate(int size, int arg) {        T[] result = new T[size];        foreach(ref el; result)            el=new T(arg);        return result;    }}

Then you can allocate an entire array of 10 elements at once with:

A[] a = allocate!(A)(10, 5);

Of course this has fixed constructor arguments, but you could probably do something with variadic arguments to the template and some mixins to generate the correct constructor call.