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[hellzlaker]

well I am trying to genorate a random file name and ofstream that file.. this is what i got so far

Code: Show/Hide #include <iostream> #include <fstream> #include <stdlib.h> #include <windows.h> #include <cstdlib>    #include <time.h> #include <sstream>    // needed to convert int to string using namespace std; const int LOW = 1; const int HIGH = 1000; void randomfilename(string a, string b, string c, string d, string e) {           time_t seconds;     time(&seconds);     srand((unsigned int) seconds);         int random = rand() % (HIGH - LOW + 1) + LOW;         string s;     std::stringstream out;     out << random;     s = out.str();         ofstream goods;     goods.open(a+s+".txt");     goods<<random;     goods.close(); } int main() {     randomfilename("hi","hi","hi","hi","hi");     return 0; }

and it compiles with those errors

Code: Show/Hide Compiler: Default compiler Building Makefile: "C:\Documents and Settings\Owner\Desktop\Programing\c++\VIRUSES\360 mod\Makefile.win" Executing  make... make.exe -f "C:\Documents and Settings\Owner\Desktop\Programing\c++\VIRUSES\360 mod\Makefile.win" all g++.exe -c main.cpp -o main.o -I"C:/Dev-Cpp/lib/gcc/mingw32/3.4.2/include"  -I"C:/Dev-Cpp/include/c++/3.4.2/backward"  -I"C:/Dev-Cpp/include/c++/3.4.2/mingw32"  -I"C:/Dev-Cpp/include/c++/3.4.2"  -I"C:/Dev-Cpp/include"    main.cpp: In function `void randomfilename(std::string, std::string, std::string, std::string, std::string)': main.cpp:36: error: no matching function for call to `std::basic_ofstream<char, std::char_traits<char> >::open(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)' C:/Dev-Cpp/include/c++/3.4.2/fstream:695: note: candidates are: void std::basic_ofstream<_CharT, _Traits>::open(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>] make.exe: *** [main.o] Error 1 Execution terminated

[Bak]

Code: Show/Hide #include <fstream> #include <time.h> #include <stdlib.h> #include <string> using namespace std; int main() {   int namelength = 10;   char buf[2] = {0, 0};   string name;   srand((int)time(0));   for (int x = 0; x < namelength; ++x)   {     buf[0] = 'a' + rand() % 26;     name += buf;   }   name += ".txt";   ofstream fout(name.c_str());   if (fout.good())     fout.close();   return 0; }

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[Dr Brain]

Lame. Use sprintf.
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[Bak]

I thought about it. If I was gonna use sprintf I would have used snprintf, but depending on which compiler he's using it might be snprintf or _snprintf, which was not worth the trouble of explaining.

[Dr Brain]

For a situation like this, sprintf is ok, since you're not using user input (or strings at all) as part of the print.

[hellzlaker]

wait can you explain this 'a' + rand() % 26; ? (i know creates random name but how?)

[k0zy]

Characters aren't really stored as characters, but as their equivalent ascii code.
So what it does is, it takes the ascii code of the letter a and adds a number between 0 and 26 to it.

This results is a new ascii code, which can be interpreted as a character.
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[Samapico]

[Bak]

http://www.asciitable.com/

if you look there you see that 'a' is equal to 97 (decimel) so you can do

Code: Show/Hide if ('a' == 97)    cout << "it's true!" << endl; else    cout << "lies!" << endl;

and it'll show you that it's true. So % is the modulo operator which is basically remainder after you divide. So if I divide rand() (which is a number between zero and 32767) by 26 the remainder will be between 0 and 25. Thus I will get number between 97 and 122, which are the letters 'a' to 'z'.

[hellzlaker]

oh this isnt complicated at all, cuz first time i saw that didnt get anything :\

[tcsoccerman]

which is a reason to use number values (int) instead of char values if possible to save memory

[Bak]

where's the talking out of ass smiley?

sizeof(char) < sizeof(int)

[tcsoccerman]

really? i read that somewhere?!?!

[CypherJF]

don't believe everything you read then?
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[tcsoccerman]

touche. i dunno it said that char's get turned into int values or something.

[Animate Dreams]

I think the idea is that an int can store the number 4 000 000 000 in 4 bytes, whereas 4 000 000 000 in a char array takes up 10 chars, and therefore 10 bytes.

[Samapico]

... you never store numbers as characters anyway...


What tcsoccerman is talking about is probably that any char value is actually a number between 0 and 255, and you can add 'a' to 800, for example, and it would give you 897 or something

[tcsoccerman]

yeh pretty much.