Probably you've come over this problem once in a while, too.
You have a repeating solution, so you use a for(each) loop.
Sometimes, there is an action to be performed between the end of one iteration and the beginning of the next, if there is one. The prime example is printing the comma when printing a list: There is one between any two elements, but neither is one at front or behind the last one.

Typical solutions I employed were:
1 Handling the first element separately
2 Condition in the loop, that is false exactly for the first iteration.

1 can be done with ranges easily:

if (!range.empty)
{
    action(range.front);
    range.popFront;
    foreach (element; range)
    {
        betweenAction();
        action(element);
    }
}

This approach is clearly quite verbose for the problem, but there's nothing done unnecessarily.

2 can be done easily, too:

foreach (i, element; range)
{
    if (i > 0) betweenAction();
    action(element);
}

While 2 is less code, it's prone to be checked every iteration.
Note that 2 is rather D specific in its length. It can be done in other languages, but is more verbose.

Is there a cleaner solution that I missed?

On Thursday, 4 July 2019 at 17:00:33 UTC, Q. Schroll wrote:
> Probably you've come over this problem once in a while, too.
> You have a repeating solution, so you use a for(each) loop.
> Sometimes, there is an action to be performed between the end of one iteration and the beginning of the next, if there is one. The prime example is printing the comma when printing a list: There is one between any two elements, but neither is one at front or behind the last one.
>
> Typical solutions I employed were:
> 1 Handling the first element separately
> 2 Condition in the loop, that is false exactly for the first iteration.
>
> 1 can be done with ranges easily:
>
> if (!range.empty)
> {
>     action(range.front);
>     range.popFront;
>     foreach (element; range)
>     {
>         betweenAction();
>         action(element);
>     }
> }
>
> This approach is clearly quite verbose for the problem, but there's nothing done unnecessarily.
>
> 2 can be done easily, too:
>
> foreach (i, element; range)
> {
>     if (i > 0) betweenAction();
>     action(element);
> }
>
> While 2 is less code, it's prone to be checked every iteration.
> Note that 2 is rather D specific in its length. It can be done in other languages, but is more verbose.
>
> Is there a cleaner solution that I missed?

As far as I can interpret it, joiner

https://dlang.org/library/std/algorithm/iteration/joiner.html

uses roughly the first approach.

On Thursday, 4 July 2019 at 17:00:33 UTC, Q. Schroll wrote:
> The prime example is printing the comma when printing a list: There is one between any two elements, but neither is one at front or behind the last one.

If it is just for printing commas in between, you can use range.join(", ")

https://dlang.org/phobos/std_array.html#.join

On Saturday, 6 July 2019 at 11:48:42 UTC, berni wrote:
> On Thursday, 4 July 2019 at 17:00:33 UTC, Q. Schroll wrote:
>> The prime example is printing the comma when printing a list: There is one between any two elements, but neither is one at front or behind the last one.
>
> If it is just for printing commas in between, you can use range.join(", ")
>
> https://dlang.org/phobos/std_array.html#.join

.map!(e=>e.text).join( ", "); // map for non strings
or
.format!"%(%s, %)"; // for anything