I have a that function returns an sf::EventType based on a string provided by a user. If there is no match, the functions returns sf::nullopt. But I would like to print a suggested, valid, sf::EventType, that is the closest to what the user provided, to help with misspellings etc.
There are 'only' 13 valid sf::EventType's that have to be checked for the closest match, and i'm assuming that a user wont enter some ridiculusly long string.
On my laptops m3-7Y30 intel processor I have tested the functions speed on both debug and release mode:
~45 seconds on debug ~3 seconds on release
Huge difference, but still I feel like 3 seconds is a bit much given that the user might provide anywhere from 5 to 100 event types.
Given these results I doubt that this approach to suggest a valid sf::EventType could be optimized enough to make it viable, but if it can, I would like to know how. If not, I would like a suggestion for an alternative, that would still print a suggestion, no matter how far off the provided string is.
The relevant code looks like this:
convertToSfEvent
std::optional<sf::Event::EventType> EventFileReader::convertToSfEvent(std::string_view event)
{
if (event == "Closed") return sf::Event::EventType::Closed;
else if (event == "Resized") return sf::Event::EventType::Resized;
else if (event == "LostFocus") return sf::Event::EventType::LostFocus;
else if (event == "GainedFocus") return sf::Event::EventType::GainedFocus;
else if (event == "TextEntered") return sf::Event::EventType::TextEntered;
else if (event == "KeyPressed") return sf::Event::EventType::KeyPressed;
else if (event == "KeyReleased") return sf::Event::EventType::KeyReleased;
else if (event == "MouseWheelScrolled") return sf::Event::EventType::MouseWheelScrolled;
else if (event == "MouseButtonPressed") return sf::Event::EventType::MouseButtonPressed;
else if (event == "MouseButtonReleased") return sf::Event::EventType::MouseButtonReleased;
else if (event == "MouseMoved") return sf::Event::EventType::MouseMoved;
else if (event == "MouseEntered") return sf::Event::EventType::MouseEntered;
else if (event == "MouseLeft") return sf::Event::EventType::MouseLeft;
else
{
// Heres is where I search for a match, and the recursion madness starts
auto smallest_required_change{ INT_MAX };
auto closest_string{ std::string() };
for (auto event_type : this->event_types)
{
auto result{ levensteinDistance(event, event_type, event.length(), event_type.length()) };
if (result < smallest_required_change)
{
smallest_required_change = result;
closest_string = event_type;
}
}
std::cerr << "Could not recognize event_type token: '" << event << "' did you mean: '" << closest_string << "'?" << "\n";
return std::nullopt;
}
}
levensteinDistance
std::size_t EventFileReader::levensteinDistance(std::string_view first, std::string_view second, std::size_t first_pos, std::size_t second_pos)
{
static auto one{ std::size_t(1) };
if (!first_pos)
return first_pos;
if (!second_pos)
return second_pos;
if (first[first_pos - one] == second[second_pos - one])
return levensteinDistance(first, second, first_pos - one, second_pos - one);
return 1 + std::min({ levensteinDistance(first, second, first_pos, second_pos - one),
levensteinDistance(first, second, first_pos - one, second_pos),
levensteinDistance(first, second, first_pos - one, second_pos - one)
});
}
Your levenshtein
implementation is recursive and slow, you may want to change that to a faster one, for example (source: https://rosettacode.org/wiki/Levenshtein_distance):
// Compute Levenshtein Distance
// Martin Ettl, 2012-10-05
size_t uiLevenshteinDistance(const std::string &s1, const std::string &s2)
{
const size_t m(s1.size());
const size_t n(s2.size());
if( m==0 ) return n;
if( n==0 ) return m;
size_t *costs = new size_t[n + 1];
for( size_t k=0; k<=n; k++ ) costs[k] = k;
size_t i = 0;
for ( std::string::const_iterator it1 = s1.begin(); it1 != s1.end(); ++it1, ++i )
{
costs[0] = i+1;
size_t corner = i;
size_t j = 0;
for ( std::string::const_iterator it2 = s2.begin(); it2 != s2.end(); ++it2, ++j )
{
size_t upper = costs[j+1];
if( *it1 == *it2 )
{
costs[j+1] = corner;
}
else
{
size_t t(upper<corner?upper:corner);
costs[j+1] = (costs[j]<t?costs[j]:t)+1;
}
corner = upper;
}
}
size_t result = costs[n];
delete [] costs;
return result;
}
Or you may check this page for the inspiration: https://en.wikibooks.org/wiki/Algorithm_Implementation/Strings/Levenshtein_distance#C