Dont understand error message

**KIBO** · 04-15-2008

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

Code:

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

the message is:

1>d:\dev\projects\dirwatcher\dirwatcher\dirwatcher .cpp(27) : error C2784: 'std::_String_iterator<_Elem,_Traits,_Alloc> std:

perator +(_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'

**matsp** · 04-15-2008

Did you include <string>?

--
Mats

**KIBO** · 04-16-2008

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:

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

**CornedBee** · 04-16-2008

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.

**matsp** · 04-16-2008

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.

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.

--
Mats

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