Dave's Brain

Browse - programming tips - stl map rename key

Date: 2009oct21
Language: C/C++

Q.  How can I rename a std::map<> key?

A. Assuming these declarations:

	typedef std::map<std::string, int, std::less<std::string> > StringToInt;
	StringToInt	m;

You might first try this:

	StringToInt::iterator		it;
	it = m.find("something");
	it->first = "something else";	// WRONG!!!

This doesn't work because it->first is a const.

So do this:

	bool rename_key(const std::string old_key, const std::string new_key)
	{
		StringToInt::iterator		it;

		if ((it = m.find(old_key)) == m.end()) return false;
		m.insert(StringToInt::value_type(new_key, it->second));
		m.erase(it);
		return true;
	}

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