collect

static VALUE
lazy_map(VALUE obj)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eArgError, "tried to call lazy map without a block");
    }

    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         lazy_map_func, 0),
                           Qnil, lazy_receiver_size);
}