How to use "String.h" library in MFC visual C++

This is a discussion on How to use "String.h" library in MFC visual C++ within the C++ Programming forums, part of the General Programming Boards category; I use WinConsle Application in visual Studio C++ to write code,but I can't use "string.h" ,compiler inform that "string undeclared ...

  1. #1
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    Post How to use "String.h" library in MFC visual C++

    I use WinConsle Application in visual Studio C++ to write code,but I can't use "string.h" ,compiler inform that "string undeclared identifier" although in folder "Include" of VC++ ,I had this file(string.h)

    Code:
    #include <iostream.h>
    #include <fstream.h>
    #include <stdlib.h>
    #include <iomanip.h>
    #include <conio.h>
    #include <string.h>
    //const char file.out[]="C://thu.txt";
    //void outputline (int acc,const char*name,double bal){
    	/*cout<<setiosflags(ios::left)<<setw(10)<<acc
    		<<setw(13)<<name<<setw(7)<<setprecision(3)
    		<<resetiosflags(ios::left)
    		<<setiosflags(ios::fixed| ios::showpoint)
    		<<bal<<'\n'<<flush;*/
    void outputline(int acc){
    	cout<<acc<<endl;
    }
    void main()
    {
    	string a = "abcd";//Error at this line,don't understand  string
    	int i = a.length;
    	cout<<i;
        ofstream outputfile(file.out,ios::out);
        if(!outputfile){
            cerr<<"File not found";
            exit(1);
        }
        int account,acc;
        char name[30];
        float balance;
        //while (cin>>account>>name>>balance){
            /*outputfile <<account<<' '<<name
                        <<' ' <<balance<<'\n'<<flush;*/
    	while (cin>>account)
    		//Viet du lieu ra file
    		outputfile <<account<<flush;
            //cout<<"?";
    
    	ifstream inFile("C://thu.txt");
    	if (!inFile){
    		cerr<<"File not found\n";
    		exit(1);
    }
    
    /*	int acc;
    	char name[30];
    	double bal;
    
    	cout<<setiosflags(ios::left)<<setw(10)<<"Account"
    		<<setw(13)<<"Name"<<"Balance\n"<<flush;*/
    	/*while(inFile>>acc>>name>>bal)
    		outputline(acc,name,bal);*/
    	
    	while(inFile>>acc && (!inFile.eof()))
    		outputline(acc);
    	getch();
    }
    Whoever show me how to use "string.h" file in Win Console??Thanks very much
    Last edited by Ken Fitlike; 09-28-2006 at 08:38 AM. Reason: added code tags

  2. #2
    ZuK
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    Looks like you want to use std::string.
    The right header would be
    Code:
    #include <string>
    using string.h just declares the c-string ( char arrays ) functions.
    Kurt

  3. #3
    (?<!re)tired Mario F.'s Avatar
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    You are trying to include the C style string header that declares functions such as strcmp and strcpy.

    The header you want is <string>

    Also use code tags too please. It's not fun to have to read your code as is.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  4. #4
    Its hard... But im here swgh's Avatar
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    Code:
    void main
    is outdated, I am suprised MSVC++ lets you use this.
    Change it to
    Code:
    int main ( void )
    as it more to the standard. Also, you shuold of at least had a compiler warning about this, unless you have set it on a low level.

  5. #5
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    I think void main() or int main() is Ok,compiler in MFC Win Consolse C++ doesn't catch them .
    Quote Originally Posted by ZuK
    Looks like you want to use std::string.
    The right header would be
    Code:
    #include <string>
    using string.h just declares the c-string ( char arrays ) functions.
    Kurt
    I have this error and when I edit like you typed,It is true..thanks for Zuk...
    But I don't understand why I can type #include <iostream.h> but to use string.h I have to type
    " #include <string>
    using std::string;"
    Thanks for helping of everybody......
    Last edited by zaracattle; 09-28-2006 at 09:29 AM.

  6. #6
    C++ Witch laserlight's Avatar
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    What is the current code that you are working with?
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  7. #7
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    Quote Originally Posted by laserlight
    What is the current code that you are working with?
    This code is only code for me to try "string.h" library ,thanks for your interest....

  8. #8
    C++ Witch laserlight's Avatar
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    But I don't understand why I can type #include <iostream.h> but to use string.h I have to type
    " #include <string>
    using std::string;"
    Might be a compiler quirk. You should #include <iostream>, not <iostream.h>
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  9. #9
    (?<!re)tired Mario F.'s Avatar
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    string.h is for C-Style string functions. Not for std::string functions. Your code indicates you are using std::string in this line:

    Code:
    string a = "abcd";
    That is a C++ style string. And the way to use it is to include <string>, not <string.h>. You also have to code:

    Code:
    std::string a = "abcd";
    Instead of what you had before. This is so because the type string is included inside the namespace std. If you don't like to have to add std:: to every instance of string, you can put using namespace std; just before main().

    If on the other side you are indeed wanting to use C-Style strings, not the C++ ones. Then you cannot create a string with string a. You leave your include as is right now and your strings are defined like so:

    Code:
    char a[] = "abcd";
    
    or 
    
    char *a = "abcd";
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  10. #10
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    >> But I don't understand why I can type #include <iostream.h> but to use string.h I have to type

    <iostream> is the new C++ version of <iostream.h>, so for old compilers either will work relatively well.

    <cstring> is the new C++ version of <string.h>, both work on C style string functions.

    <string> has no older, pre-standard equivalent, so if you aren't including <string>, you cannot use the string class. Note that this is different than <string.h>/<cstring>.

    You should be using <iostream>, not <iostream.h> because when you move on to a modern compiler your <iostream.h> won't work any more.

  11. #11
    Cat
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    Your code hasn't been valid C++ since 1997. You might consider a somewhat newer reference to base your work off of, something that actually takes into account the 1998 standard?


    For example:
    <iostream.h> => <iostream>
    <fstream.h> => <fstream>
    <stdlib.h> => <cstdlib>
    <iomanip.h> => <iomanip>
    <string.h> => <string>

    You're missing a large number of std:: as well; your code is extremely legacy from before namespaces existed in C++.
    Last edited by Cat; 09-28-2006 at 10:26 PM.
    You ever try a pink golf ball, Wally? Why, the wind shear on a pink ball alone can take the head clean off a 90 pound midget at 300 yards.

  12. #12
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    >> <string.h> => <string>
    That's not correct, and it is the source of the OPs confusion as well.

    <string.h> => <cstring>
    nothing => <string>

    >> <conio.h> => <cconio>
    Also, conio.h is not standard, so if your compiler supports it, it is still <conio.h>.

  13. #13
    (?<!re)tired Mario F.'s Avatar
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    Also there's no evolution like the one implied in <iomanip.h> => <iomanip>

    iomanip is strictly a C++ library. Much like "iostream.h", iomanip.h is supplied by some compilers in order to provide backward compatibility.

    EDIT: Oops. Nevermind the above. Cat was addressing exactly C98 changes.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  14. #14
    Cat
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    Quote Originally Posted by Daved
    >> <string.h> => <string>
    That's not correct, and it is the source of the OPs confusion as well.

    <string.h> => <cstring>
    nothing => <string>
    Yeah, I know, I was detailing the changes he should make, not necessarily the changes made by the 1998 standard.
    You ever try a pink golf ball, Wally? Why, the wind shear on a pink ball alone can take the head clean off a 90 pound midget at 300 yards.

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