SO rotate question

[bearophile]

simendsjo:
> Suggestions for D-ifying the code is welcome.

Your unit tests are not good enough, they miss some important corner cases.
This my first version in D2:

import std.string: indexOf;

/// return True if s1 is a rotated version of s2
bool isRotated(T)(T[] s1, T[] s2) {
    return (s1.length + s2.length == 0) ||
           (s1.length == s2.length && indexOf(s1 ~ s1, s2) != -1);
}

unittest { // of isRotated
    assert(isRotated("", ""));
    assert(!isRotated("", "x"));
    assert(!isRotated("x", ""));
    assert(isRotated("x", "x"));

    string s = "rotato";
    assert(isRotated(s, "rotato"));
    assert(isRotated(s, "otator"));
    assert(isRotated(s, "tatoro"));
    assert(isRotated(s, "atorot"));
    assert(isRotated(s, "torota"));
    assert(isRotated(s, "orotat"));

    assert(!isRotated(s, "rotator"));
    assert(!isRotated(s, "rotat"));
    assert(!isRotated(s, "rotata"));
}

void main() {}

Bye,
bearophile