Dont understand error message

I get an error message on the second line and I dont understand why. Shouldnt this code compile?

Code:

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wstring s(FileName, FileNameLength);
s = wstring(L"\\") + s;

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the message is:

1>d:\dev\projects\dirwatcher\dirwatcher\dirwatcher .cpp(27) : error C2784: 'std::_String_iterator<_Elem,_Traits,_Alloc> std::operator +(_String_iterator<_Elem,_Traits,_Alloc>::differen ce_type,std::_String_iterator<_Elem,_Traits,_Alloc >)' : could not deduce template argument for 'std::_String_iterator<_Elem,_Traits,_Alloc>' from 'std::wstring'

Did you include <string>?

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Mats

lol that was the problem. been a while since I didnt understand such a basic issue. Strange though that it did work when I rewrote it to the following without including string either.

Code:

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wstring temp;
wstring s(fni.FileName, fni.FileNameLength);
temp += wstring(Dir);
temp += L"\\";
temp += s;

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That's because += is a member of std::basic_string and thus available when an internal component of the MS library include <xstring>, whereas + is a free function defined in <string>, and thus not available.

Quote:

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Originally Posted by CornedBee

That's because += is a member of std::basic_string and thus available when an internal component of the MS library include <xstring>, whereas + is a free function defined in <string>, and thus not available.

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And this implies that <xstring> gets included by some other component at some point or another - you STILL SHOULD include <string> since you are using std::(w)string - it may work as it is, but it's a bad idea to rely on it, as a different set of include files may drag in less "extras" and thus break your build.

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Mats