Re: How about a "static foreach"?

[Timon Gehr]

On 06/17/2012 03:02 AM, Mehrdad wrote:

This doesn't work:

foreach (i; 0 .. T.tupleof.length)
static if (is(typeof(T.tupleof[i]) == int)) // error!
...

because the foreach isn't static.


It forces me to write:

template Iota(size_t i, size_t n)
{
static if (n == 0) { alias TypeTuple!() Iota; }
else { alias TypeTuple!(i, Iota!(i + 1, n - 1)) Iota; }
}

foreach (i; Iota!(0, T.tupleof.length)) // "static foreach"
static if (is(typeof(T.tupleof[i]) == int))
...

which gets annoying quickly.


Why not just let us write

static foreach (i; 0 .. T.tupleof.length)
static if (is(typeof(T.tupleof[i]) == int))
...

so that the code is a lot more succinct and easy to write?

Last time I asked, the answer was that static foreach had been part of
the plan, but Walter experienced implementation problems.

I don't think there is any reason why there is no static foreach except
for the fact that someone would need to implement it.