do not throw when manipulating with sets in regexp

alib2/src/regexp/RegExp.cpp

@@ -64,7 +64,7 @@ RegExp& RegExp::operator=(const RegExp& other) {
 RegExp& RegExp::operator=(RegExp&& other) noexcept {
 	std::swap(this->regExp, other.regExp);
-
+	std::swap(this->alphabet, other.alphabet);
 	return *this;
 }
@@ -98,10 +98,8 @@ const std::set<alphabet::Symbol>& RegExp::getAlphabet() const {
 	return alphabet;
 }
-void RegExp::addSymbolToAlphabet(const alphabet::Symbol & symbol) {
-	std::pair<std::set<alphabet::Symbol>::iterator, bool> ret = alphabet.insert(symbol);
-	if (!ret.second)
-		throw alib::AlibException("Symbol \"" + (std::string) symbol + "\" is already in the alphabet.");
+bool RegExp::addSymbolToAlphabet(const alphabet::Symbol & symbol) {
+	return alphabet.insert(symbol).second;
 }
 void RegExp::setAlphabet(const std::set<alphabet::Symbol> & symbols) {
@@ -116,13 +114,11 @@ void RegExp::setAlphabet(const std::set<alphabet::Symbol> & symbols) {
 	this->alphabet = symbols;
 }
-void RegExp::removeSymbolFromAlphabet(const alphabet::Symbol & symbol) {
+bool RegExp::removeSymbolFromAlphabet(const alphabet::Symbol & symbol) {
 	if(this->regExp->testSymbol(symbol))
 		throw alib::AlibException("Input symbol \"" + (std::string) symbol + "\" is used.");
 	
-	int removed = alphabet.erase(symbol);
-	if (!removed)
-		throw alib::AlibException("Input symbol \"" + (std::string) symbol + "\" doesn't exist.");
+	return alphabet.erase(symbol);
 }
 bool RegExp::isEmpty() const {

alib2/src/regexp/RegExp.h

@@ -79,7 +79,7 @@ public:
 	 * Adds symbol to the alphabet available in the regular expression
 	 * @param symbol new symbol added to the alphabet
 	 */
-	void addSymbolToAlphabet(const alphabet::Symbol & symbol);
+	bool addSymbolToAlphabet(const alphabet::Symbol & symbol);
 	/**
 	 * Sets the alphabet of the regular expression
@@ -91,7 +91,7 @@ public:
 	 * Removes symbol from the alphabet of symbol available in the regular expression
 	 * @param symbol removed symbol from the alphabet
 	 */
-	void removeSymbolFromAlphabet(const alphabet::Symbol & symbol);
+	bool removeSymbolFromAlphabet(const alphabet::Symbol & symbol);
 	
 	/**
 	 * @return true if regexp represents empty language