fix gui build

src/gui/PivotGui.cpp

@@ -25,7 +25,7 @@ static std::string PrintVect(const Vect& vect) {
 		Matrix vector = vect.GetVector(i);
 		result += " (";
 		for (std::size_t j = 0; j < vect.GetDimension(); j++) {
-			result += vector.at(j, 0).ToString() + ", ";
+			result += std::to_string(static_cast<int>(vector.at(j, 0))) + ", ";
 		}
 		result += " ), ";
 	}
@@ -136,7 +136,7 @@ void PivotGui::Render() {
 		for (size_t i = 0; i < linearSystem.GetRawCount(); ++i) {
 			for (size_t j = 0; j < linearSystem.GetColumnCount(); ++j) {
 				equationsResultImage +=
-					linearSystem.at(i, j).ToString() + "*" + std::string {static_cast<char>('a' + j)} + " + ";
+					std::to_string(static_cast<int>(linearSystem.at(i, j))) + "*" + std::string {static_cast<char>('a' + j)} + " + ";
 			}
 			equationsResultImage = equationsResultImage.substr(0, equationsResultImage.size() - 3) + " = 0\n";
 		}