Re: Static Length Propagation of Ranges

[Nordlöw via Digitalmars-d-learn]

On Wednesday, 19 October 2016 at 19:39:46 UTC, Nordlöw wrote:

On Wednesday, 19 October 2016 at 19:01:50 UTC, Meta wrote:

https://goo.gl/t9m3YK

I'm actually pretty impressed that this kind of code can be written in D.

Thanks! Add at

https://github.com/nordlow/phobos-next/blob/master/src/algorithm_ex.d#L2234

Made it even modular by factoring out arrayN at

https://github.com/nordlow/phobos-next/blob/master/src/algorithm_ex.d#L2200

and used at

https://github.com/nordlow/phobos-next/blob/master/src/algorithm_ex.d#L2215

Code:


ElementType!R[n] arrayN(size_t n, R)(R r)
{
    assert(r.length == n);
    typeof(return) dst;
    import std.algorithm.mutation : copy;
    r.copy(dst[]);
    return dst;
}

typeof(fun(E.init))[n] map(alias fun, E, size_t n)(const E[n] src)
{
    import std.algorithm.iteration : map;
    return src[].map!fun.arrayN!n;
}

@safe pure nothrow unittest
{
    import std.meta : AliasSeq;
    foreach (E; AliasSeq!(int, double))
    {
        enum n = 42;
        E[n] c;
        const result = map!(_ => _^^2)(c);
        static assert(c.length == result.length);
        static assert(is(typeof(result) == const(E)[n]));
    }
}