Programming Forums > Application Development > C++

Kilo · May 22nd, 2006, 12:08 PM

I hate my life...

Im havig some issues with adding strings together.. i do not want to use a char array! i want to add 2 actual strings together!

my code

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void Engine::AddError(bool lineAdd, int lineNum, std::string error)
{
	std::string s_tempError;

	if(lineAdd == true)
	{
		strcat(s_tempError, "[LINE#");
	}

	strcat(s_tempError, (char)lineNum);

	strcat(s_tempError, error); 

	s_errorArray.push_back(s_tempError);
}

the errors:

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1>------ Build started: Project: SED, Configuration: Debug Win32 ------
1>Compiling...
1>SED.cpp
1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(38) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char *'
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(41) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char *'
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(43) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char *'
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(74) : warning C4018: '<=' : signed/unsigned mismatch
1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(95) : warning C4018: '<=' : signed/unsigned mismatch
1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(115) : warning C4018: '<=' : signed/unsigned mismatch
1>Build log was saved at "file://c:\Documents and Settings\knowell\My Documents\Visual Studio 2005\Projects\SED\SED\Debug\BuildLog.htm"
1>SED - 3 error(s), 3 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

jayme · May 22nd, 2006, 12:12 PM

I just threw this together real quick.

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#include <iostream>
#include <cstring>
using namespace std;

int main()
{
    string hel, lo;
    hel = "hel";
    lo = "lo";

    hel+=lo;
    cout << hel;
    return 0;
}

It explains itself, so I'll just leave it at that.

Jessehk · May 22nd, 2006, 12:15 PM

strcat() is only used for char arrays (C-style strings).

Simply use the += operator or std::string::append() to add together std::strings.

DaWei · May 22nd, 2006, 12:30 PM

Take about thirty seconds and distinguish in your mind, forever, the difference between a C-string (null terminated array of char) and a "C++" string, which encapsulates that with methods, hidden and otherwise, that serve you breakfast in bed. It'll save you a lot of time and grief.

May 22nd, 2006, 12:08 PM	#1
Kilo Expert Programmer Join Date: Nov 2005 Location: In Pink Clam? Posts: 542 Rep Power: 0	strcat() && char array[10] && stupid! I hate my life... Im havig some issues with adding strings together.. i do not want to use a char array! i want to add 2 actual strings together! my code (Toggle Plain Text) void Engine::AddError(bool lineAdd, int lineNum, std::string error) { std::string s_tempError; if(lineAdd == true) { strcat(s_tempError, "[LINE#"); } strcat(s_tempError, (char)lineNum); strcat(s_tempError, error); s_errorArray.push_back(s_tempError); } void Engine::AddError(bool lineAdd, int lineNum, std::string error) { std::string s_tempError; if(lineAdd == true) { strcat(s_tempError, "[LINE#"); } strcat(s_tempError, (char)lineNum); strcat(s_tempError, error); s_errorArray.push_back(s_tempError); } the errors: (Toggle Plain Text) 1>------ Build started: Project: SED, Configuration: Debug Win32 ------ 1>Compiling... 1>SED.cpp 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(38) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char ' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(41) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char ' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(43) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char ' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(74) : warning C4018: '<=' : signed/unsigned mismatch 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(95) : warning C4018: '<=' : signed/unsigned mismatch 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(115) : warning C4018: '<=' : signed/unsigned mismatch 1>Build log was saved at "file://c:\Documents and Settings\knowell\My Documents\Visual Studio 2005\Projects\SED\SED\Debug\BuildLog.htm" 1>SED - 3 error(s), 3 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== 1>------ Build started: Project: SED, Configuration: Debug Win32 ------ 1>Compiling... 1>SED.cpp 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(38) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char ' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(41) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char ' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(43) : error C2664: 'strcat' : cannot convert parameter 1 from 'std::string' to 'char ' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(74) : warning C4018: '<=' : signed/unsigned mismatch 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(95) : warning C4018: '<=' : signed/unsigned mismatch 1>c:\documents and settings\knowell\my documents\visual studio 2005\projects\sed\sed\sed.cpp(115) : warning C4018: '<=' : signed/unsigned mismatch 1>Build log was saved at "file://c:\Documents and Settings\knowell\My Documents\Visual Studio 2005\Projects\SED\SED\Debug\BuildLog.htm" 1>SED - 3 error(s), 3 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== __________________ "When in Rome, Do as the Romans Do" "Beauty is in the eye of the BEER holder" "Save your breath your going to need it for your blow up doll later" SearchLores.org

May 22nd, 2006, 12:15 PM	#3
Jessehk The Oblivious One Join Date: May 2005 Location: Ontario, Canada Posts: 648 Rep Power: 4	strcat() is only used for char arrays (C-style strings). Simply use the += operator or std::string::append() to add together std::strings. __________________ Dr. Zoidberg: [ecstatic] I'm going to a movie... with FRIENDS!

May 22nd, 2006, 12:30 PM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Take about thirty seconds and distinguish in your mind, forever, the difference between a C-string (null terminated array of char) and a "C++" string, which encapsulates that with methods, hidden and otherwise, that serve you breakfast in bed. It'll save you a lot of time and grief. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Programming Forums > Application Development > C++

strcat() && char array[10] && stupid!