Method substr

tests/framework/src/doctest.cpp:663–669

}

String String::substr(size_type pos, size_type cnt) && {
    cnt = std::min(cnt, size() - 1 - pos);
    char* cptr = c_str();
    memmove(cptr, cptr + pos, cnt);
    setSize(cnt);
    return std::move(*this);
}

String String::substr(size_type pos, size_type cnt) const & {
    cnt = std::min(cnt, size() - 1 - pos);