std::mismatch compile time error

[morando]

I made some compare (case insensitive) function to be able to compare some file & folder names, since it would be logical to make params const i got compile time error.

bool ci_compare(const std::wstring& l, const std::wstring& r)
{
	const std::locale loc("");
	std::pair< std::wstring::iterator, std::wstring::iterator > result;
	result = std::mismatch(l.begin(), l.end(), r.begin(), 
	[&loc] (std::wstring::value_type chl, std::wstring::value_type chr)
	{ return std::toupper(chl, loc) == std::toupper(chr, loc); } );
        return l.end() == result.first;
}

quoted first line that has error:

error C2664: 'std::_String_iterator<_Elem,_Traits,_Alloc>::_String_iterator(const std::_String_iterator<_Elem,_Traits,_Alloc> &)' : cannot convert parameter 1 from 'std::_String_const_iterator<_Elem,_Traits,_Alloc>' to 'const std::_String_iterator<_Elem,_Traits,_Alloc> &'

How to resolve this? Beside removing const-ness from params.

Thanks for your time.

[Athar]

By using const_iterators:
std::pair< std::wstring::const_iterator, std::wstring::const_iterator > result;

[morando]

Thats it. Thanks.