grep

static VALUE
lazy_grep(VALUE obj, VALUE pattern)
{
    return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
                                         rb_block_given_p() ?
                                         lazy_grep_iter : lazy_grep_func,
                                         pattern),
                           rb_ary_new3(1, pattern), 0);
}