Srand time null ошибка

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int main()
{
   srand(time(0));
}

#include <iostream> //use iostream not iostream.h (.h is the c version)
#include <ctime>
using namespace std;

class Horse
{
	int position;
	int random;

	public:

	Horse(){}; //note the two curly brackets (this is the default constructor that is made if you do not include a constructor)

	void advance()
	{
		random = rand() % 2;
		cout << random;
	}

	int getPosition( int y )
	{
		return y;
	}

};

int main()
{
	srand(time(0));//seed your random here.
	Horse test;
	test.advance();

	return 0;
}

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• srand(time(NULL)) error message

1. srand(time(NULL)) error message
   

   Hi
   I’m not a programmer, but I want to get some C code to work for some study that I’m doing in cognitive psychology. It’s a mathematical model; it does a calculation and returns a value. The code was written in 1996, and when I try to compile it (I’m typing gcc filename), I get a number of error messages. The main one relates to the random number generator.
   The original code was:

   Code:

    #include "ran1.c"
   /* random seed */
   long     IDUM    = -3;

   I have replaced only the first line with:

   Code:

   #include <time.h>
   
   srand(time(NULL));
   int r = rand();

   but I get this message:

   Code:

   43:7: error: expected declaration specifiers or �...� before �time�
   
   44:1: error: initialiser element is not constant

   I think I’m heading in the right direction, but I don’t know enough about programming to get it right. I really don’t want it to return the wrong value.
   Any help would be appreciated. Thank you.

   ---

2. Re: srand(time(NULL)) error message
   

   It would be immensely helpful to see the actual implementation you have versus a snip of code as you have provided.

   A simple example of using srand() and rand() would be something like:

   Code:

   #include <stdlib.h>
   #include <time.h>
   
   const unsigned int MAX_NUM = 1000;
   
   int main()
   {
       srand(time(NULL));
   
       unsigned int num = rand() % MAX_NUM;   // num can range from 0 through (MAX_NUM - 1)
   }

   ---

3. Re: srand(time(NULL)) error message
   

   Just a note of caution about PRNGs — based on the name (ran1.c) and the negative-long seed (IDUM) it looks like you are trying to replace the Numerical Recipes implementation? If so, that’s a long-period floating point PRNG — depending what your model is doing (and how many times it’s doing it) the system rand() may or may not be a suitable replacement.

   ---

4. Re: srand(time(NULL)) error message
   

   Thanks for your helpful comments. Any information I can gather is helpful.

   Originally Posted by dwhitney67
   

   It would be immensely helpful to see the actual implementation you have versus a snip of code as you have provided.

   Does this make it clearer?
   model.txt
   The attached model.txt file is the C code that I think might be relevant. I’ve just killed about 2/3 of the lines from the middle of the file.

   Just to recap, when I tried to compile this, I got an error message in relation to the random generator.
   Thank you.

   Last edited by lisati; March 9th, 2013 at 04:34 AM.

   Reason: Change HTML tags to QUOTE

   ---

5. Re: srand(time(NULL)) error message
   

   Is there any particular reason you need to replace the original Numerical Recipes ran1 implementation? The license terms are not onerous afaik

   http://apps.nrbook.com/c/index.html

   I’d suggest including the necessary declarations and compiling the ran1.c file separately rather than doing #include «ran1.c» though

   ---

6. Re: srand(time(NULL)) error message
   

   ok, Thanks again.

   Code:

   rip@Duck:/media/win/arjuna/current_study$ gcc memnew.c
   memnew.c:22:18: fatal error: ran1.c: No such file or directory
   compilation terminated.

   Maybe I need to install something. This is Xubuntu Precise.

   ---

7. Re: srand(time(NULL)) error message
   

   If it’s the routine I think it is, you would need to get it from Numerical Recipes

   If you buy the book, you can just type it in (it’s only ~ 50 lines of code) — or you can get an electronic subscription

   http://www.nr.com/aboutNR3electronic.html

   ---

8. Re: srand(time(NULL)) error message
   

   ---

9. ran1.c includes base.h
   

   The code I have ran1.c includes:
   Where do I look for that?
   Am I on the right track?

   I’d suggest including the necessary declarations and compiling the ran1.c file separately rather than doing #include «ran1.c» though

   I’m not sure what the necessary declarations are. I’m very low level here. As I say, I’m interested in a mathematical model in cognitive psychology, I’m not a programmer.
   Thanks again.

   ---

10. error in fprintf: should be struct
    

    Hello
    I’m asking for help with format in C. The code has this line:

    Code:

     fprintf( OUTD , "%s" , SPARAM[ i ] );

    And the error is:

    HTML Code:

    format �%s� expects argument of type �char *�, but argument 3 has type �struct PARAM� [-Wformat]

    And I think you might need to know this:

    Code:

    /* strings used by the program */
    #define  NPARAM 12
    struct PARAM
    {
      char *word;
    } SPARAM[ NPARAM ] =
    {
      "Length          ",
      "Strength        ",
      "Frequency       ",
      "Criterion Used  ",
      "Criterion ROC   ",

    I’ve cut it short here, but I think that’s enough.

    I can see what the problem is, but my programming ability is very low level, and I have no idea about C. I need to change the «%s», right?
    I need to get this old C code working. Fortunately, I’ve had some good help here, and this is the only error message left.
    Comments gratefully received.

    ---

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