#ifndef _rngs_h
#define _rngs_h
#include <stdio.h>
/*
 * -------------------------------------------------------------------------- 
 * This is a Turbo Pascal unit for random number generation.  The use of this 
 * unit is recommended as a replacement for the Turbo Pascal function Random  
 * and procedure Randomize - particularly in simulation applications where    
 * the statistical 'goodness' of the random number generator is important.    
 *                                                                            
 * The generator upon which this unit is based is a so-called 'Lehmer random  
 * number generator' which returns a pseudo-random real number uniformly      
 * distributed between 0.0 and 1.0.  The period is (m - 1) where              
 * m = 2,147,483,647 and the smallest and largest possible values are (1 / m) 
 * and 1 - (1 / m) respectively.  For more details see -                      
 *                                                                            
 *        "Random Number Generators: Good Ones Are Hard To Find"              
 *                   Steve Park & Keith Miller                                
 *           Communications of the ACM, October, 1988                         
 *                                                                            
 * This unit actually supplies 256 different "streams" of random numbers.     
 * The procedure Select_Stream can be used to switch between streams.         
 *                                                                            
 * Note that a math co-processor is assumed.  To use this unit without a math 
 * co-processor, change all instances of 'double' to 'real' and change the    
 * compiler directive from $N+ to $N-.                                        
 *                                                                            
 * Note that as of 1-08-91 the multiplier used in this unit has been changed  
 * from the previous "minimal standard" 16807 to a new value of 48271.  To    
 * use this unit in its old (16807) form change the constants 'a', 'check'    
 * and 'a256' as indicated in the implementation section comments.            
 *                                                                            
 * -------------------------------------------------------------------------- 
 * Author          : Steve Park                                               
 * Language        : Turbo Pascal, 5.0                                        
 * Latest Revision : 2-19-92                                                  
 * Reference       : Lecture Notes on Simulation, by Steve Park               
 * -------------------------------------------------------------------------- 
 * C Translation By : Tracey A. Beauchat
 * -------------------------------------------------------------------------- 
 */


void initialize(void);
    /*
     * This function should be called before calling any other function
     * in the RNGS library.  It initializes the streams with default
     * values.
     *
     */
     

double Random(void);
    /*
     * Random is a Lehmer generator which returns a pseudo-random real number
     * uniformly distributed between 0.0 and 1.0.  The period is (m - 1)     
     * where m = 2,147,483,647 and the smallest and largest possible values  
     * are (1 / m) and 1 - (1 / m) respectively.                             
     *
     */


void Select_Stream(int stream);
   /*
    * Use this (optional) procedure to define the currently selected stream 
    * i.e. that stream from which the next random number will come.         
    *
    */


void Randomize(long int x);
   /*
    * Use this (optional) procedure to initialize all of the 256 random 
    * number streams according to the following conventions:            
    *                                                                   
    * if x > 0 then - x is, in fact, the initial seed                   
    * if x = 0 then - the initial seed is to be supplied interactively  
    * if x < 0 then - the initial seed is obtained from the DOS clock   
    *
    */


void Get_Seed(long int *x);
   /*
    * Use this (optional) procedure to get the current value of the random 
    * number generator seed for the currently selected stream.             
    *
    */


void Put_Seed(long int x);
#endif /* _rngs_h */