Random number??

How do I have Builder (v1.0 for win 95) generate a random number (10 digits long) then have it save it in regnum.dat??
 
thanks
4099aolAsked:
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q2guoConnect With a Mentor Commented:
#include <fstream.h>
#include <stdlib.h>

main ()
{
   unsigned int i, k;
   unsigned long random_num;
 
   ostream fout("regnum.dat");
   
   randomize();
   i = rand();
   k = rand();

   random_num = i * k;
   fout << random_num << endl;
}
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nietodCommented:
That random number won't be 10 digits long.

To get 10 digits I would use an alcoritm that gets a number that is 1 digit long and repeat it 10 times.  Like

char RndDigStr[10];

randomize();
for (int i = 0; i < 10; ++i)
   RndDigStr[i] = '0' + (rand() % 10);

this puts 10 random digits in RndDigStr.  In this case the digits are ASCII digit characters from '0' to '9'.  
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4099aolAuthor Commented:
nietod...

You said that the number will be put in the string RndDigStr, well how do I put the numbers in to the dat file?
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nietodCommented:
In my previous example you could make RndDigStr a NUL terminated sting by declaring it length 11 and adding a NUL terminator with

RndDigStr[10] = 0;

then you could output it with

fout << RndDigStr;

or you could forget RndDigStr and output each digit, like

for (int i = 0; i < 10; ++i)
   fout << (char) '0' + (rand() % 10);


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4099aolAuthor Commented:
so do this??

{                          
ostream fout("regnum.dat");
                             
char RndDigStr[10];

randomize();
for (int i = 0; i < 10; ++i)
RndDigStr[i] = '0' + (rand() % 10);
fout << RndDigStr;
}
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nietodCommented:
Not quite.

fout << RndDigStr

will work only if RndDigStr is NUL terminated.  So you would need

{
   ostream fout("regnum.dat");
                               
   char RndDigStr[11]; // Extra room for NUL.

   randomize();
   for (int i = 0; i < 10; ++i)
      RndDigStr[i] = '0' + (rand() % 10);

   RndDigStr[10] = 0; // Terminate.
   fout << RndDigStr;
}

however, if you don't need to save a copy of the digits, drop RndDigStr and just use.

{
   ostream fout("regnum.dat");
                               
   randomize();
   for (int i = 0; i < 10; ++i)
   {
      char chr = '0' + (rand() % 10);

      fout << chr;
   }
}

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4099aolAuthor Commented:
Error.  (on both sets of codes)

[C++ Error] webmaster.cpp(81): Could not find a match for 'ostream::ostream(char *)'.
[C++ Warning] webmaster.cpp(86): Conversion may lose significant digits.


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q2guoCommented:
AnsiString S;
S.SetLength(11);

randomize();

for (int i = 0; i < 10; ++i)
{
   S[i] = '0' + (rand() % 10);
}
S[10] = '\0';

TStringList *MyStringList = new TStringList;
MyStringList->Add(S);
MyStringList->SaveToFile("regnum.dat");
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4099aolAuthor Commented:
I am now getting this popup dialog box...

Project webmaste1.exe rasied exception class EOutOfMemory with message 'Out of Memory'.

I restarted my computer (thinking my computer was just running low on RAM, but had the same message.  I took the codes (that u just gave me) out and the app works fine.  Please tell me how do I get it to manage it's memory a little bit better, or fix the codes to sue less memory.
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nietodCommented:
Sorry I don't use streams so I wasn't aware that you can't print a "const char *" with a stream.  q2quo's string class solution should work.  Although I've never heard of "AnsiString", the strig supplied by STL that I'm aware of is just called "string".  But I'm not too familiare with STL.

as for th warning about loosing digits, ignore it or use the "(char)" conversion operator.  That is change

char chr = '0' + (rand() % 10);

to

char chr = (char) '0' + (rand() % 10);


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q2guoCommented:
Add
delete MyStringList;
to the end of my code
so it should read

.
.
.

TStringList *MyStringList = new TStringList;
MyStringList->Add(S);
MyStringList->SaveToFile("regnum.dat");
delete MyStringList;
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4099aolAuthor Commented:
nope still out of memory
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q2guoCommented:
Are your running above code inside a loop?
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4099aolAuthor Commented:
I do not think so, it is in FormCreate (Borland C++ Builder)
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larockdCommented:
Is randomize() a function specific to Borland?  I think I remember using it in Pascal..

Shouldn't he use srand instead to seed the random number generator?  Or does randomize in borland take care of it.  I checked on this in Visual C++ and the closest thing to randomize is randomize() when using vbscript?
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4099aolAuthor Commented:
i have no idea.
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q2guoCommented:
Try this 4099Aol

#include <vcl/classes.hpp>
#include <stdlib.h>

char S[11];
randomize();

for (int i = 0; i < 10; ++i)
{
    S[i] = '0' + (rand() % 10);
}
S[10] = '\0';

AnsiString randstring(S);

TStringList *MyStringList = new TStringList;
MyStringList->Add(S);
MyStringList->SaveToFile("regnum.dat");
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4099aolAuthor Commented:
thank you it works!
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