C++ Help: Strings

[jason2010]

I got this code here:

gLua->Msg( gLua->GetString(1) << " is a faggot.\n");

1>.\main.cpp(12) : error C2296: '<<' : illegal, left operand has type 'const char *'
1>.\main.cpp(12) : error C2297: '<<' : illegal, right operand has type 'const char [15]'

I have no idea how to do that, like in lua it's " .. " .

So FP, how'dyou do it? :byodood:

[BMCha]

[b]THIS IS WRONG IN YOUR CASE, LOOK AT THE POST BELOW ME[/b]

string+string
So your code would be:
[cpp]gLua->Msg( gLua->GetString(1) + " is a faggot.\n"); [/cpp]
And what you were looking for is called string concatenation.

--

To address what you [i]did[/i] write, the << operator is stream output, and only works with streams. You probably thought it did concatenation because it will function similarly when used with a cout (io[b]stream[/b]). You [i]will[/i] have to use it if you wish to concatenate something that isn't a string, for example, to insert a variable into a string, in which case in many cases it is advantageous to use a stringstream, like so:
[cpp]
int VarA = 17;
std::string FinalString;
std::stringstream Stream;

Stream << "Variable VarA is currently: " << VarA;
FinalString = Stream.str(); //convert to a std::string
[/cpp]

[Wyzard]

From the error message, it sounds like gLua->GetString(1) is returning a const char*, not a std::string. String concatentation doesn't work on those.

Try this instead:

gLua->Msg( std::string(gLua->GetString(1)) + " is a faggot.\n");

[jason2010]

1>.\main.cpp(11) : error C2110: '+' : cannot add two pointers :black101:

[BMCha]

[QUOTE=Wyzard;20864380]From the error message, it sounds like gLua->GetString(1) is returning a const char*, not a std::string. String concatentation doesn't work on those.[/QUOTE]

Ah, good catch, I sprung immediately to the incorrect concatenation operator and forgot to read the error message.

[jason2010]

Wyzard with your one i get this:

1>.\main.cpp(11) : error C2039: 'string' : is not a member of 'std'
1>.\main.cpp(11) : error C3861: 'string': identifier not found

[editline]01:58AM[/editline]

I did #include <string> and now I get this

1>.\main.cpp(11) : error C2664: 'ILuaInterface002::Msg' : cannot convert parameter 1 from 'std::basic_string<_Elem,_Traits,_Ax>' to 'const char *'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>,
1> _Ax=std::allocator<char>
1> ]
1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

[Wyzard]

Oops, I forgot that part. Wrap the string concatentation in parentheses and call .c_str() on the result. (Adding two strings gives you another string, and calling c_str() on that string gives you the char* that gLua-Msg() needs.)

gLua->Msg((std::string(gLua->GetString(1)) + " is a faggot.\n").c_str());

[pollyzoid]

The best way, without using std::strings or stuff.

gLua->Msg("%s is a faggot.\n", gLua->GetString(1));