Initializing a static array

[Ali Çehreli]

On 03/08/2012 06:02 PM, Hugo Florentino wrote:

 > What is the proper D syntax to initialize a static array with
 > consecutive integers starting with 1?

One of many ways:

int[N] makeArray(size_t N)()
{
     int[N] result;

     foreach (int i, ref element; result) {
         element = i;
     }

     return result;
}

void main()
{
     assert(makeArray!4() == [ 0, 1, 2, 3 ]);
}

 > I know I could simply use "for" like in C, but while reading the web
 > documentation on arrays, I noticed the vector notation. According to the
 > documentation, this code:
 > T[] a, b;
 > ...
 > a[] = b[] + 4;
 >
 > is equivalent to this code:
 > T[] a, b;
 > ...
 > for (size_t i = 0; i < a.length; i++) a[i] = b[i] + 4;

It should be possible to use a special type and keep state to achieve it 
with the arraywise syntax but this task is natural for that syntax.

 > I also tried using the array as an aggregate in a foreach statement:
 > foreach(int i, int j, myarray) j = i + 1;
 >
 > However, it does not work this way because apparently the j variable
 > seems to work only for reading, not for assigning. I wonder why this
 > limitation in behavior, if according to the documentation:
 >
 > "If there are two variables declared, the first is said to be the index
 > and the second is said to be the value [set to the elements of the
 > array, one by one]"
 >
 > So if j refers to the value,

That's the problem. j does not refer to the element, it is a copy of it. 
You must use the 'ref' keyword as in the code that I have shown above.

 > Either way, please advice the recommended D way.

There are many ways of initializing a fixed-length array with 
consecutive integers. Here is another one:

import std.algorithm;
import std.range;

void main()
{
     int[4] array = array(iota(4));
     assert(array == [ 0, 1, 2, 3 ]);
}

 >
 > Regards, Hugo

Ali

P.S. There is also the D.learn newsgroup where such threads are very 
welcome at. :)