This library provides a simple wrapper that makes the passed range head-const: it prevents reassigning the elements but otherwise does not affect their constness. This is essentially the opposite of Rebindable.

import readonly_range;

struct S {
    int field;
}

auto data = [new S(1), new S(2), new S(3)];
auto view = data.readonlyRange;
// view[0] = null; // Forbidden.
view[0].field = 13; // Allowed.
assert(data[0].field == 13);
const(S*)[ ] constView = view; // Implicit conversion.

It works by making front, back, and opIndex return the element by value—keep that in mind and avoid using it for types that are expensive to copy. Note that in the example above, data is S*[ ] so view[0] copies just the pointer, not the pointed-to object.