/* randgen.c => contains random number generator and related utilities   including advance_random, warmup_random, random, randomize*/#include "const.h"#include "type.h"#include "extern.h"#include "exfunc.h"/* GLOBAL VARIABLES */double oldrand[56];     /* array of 55 random numbers */int    jrand;          /* current random *//* FUNCTIONS */void advance_random()   /* create next batch of 55 random numbers */{  int j1;  double new_random;/*  printf("Entering Advance Random\n");*/  for (j1=1;j1<=24;j1++){    new_random = oldrand[j1] - oldrand[j1+31];    if (new_random < 0.0){      new_random = new_random + 1.0;    }    oldrand[j1] = new_random;  }  for (j1=25;j1<=55;j1++){    new_random = oldrand[j1] - oldrand[j1-24];    if (new_random < 0.0){      new_random = new_random + 1.0;    }    oldrand[j1] = new_random;  }/*  printf("leaving Advance Random\n");*/}void warmup_random(random_seed)double random_seed;{  int    j1, ii;  double new_random, prev_random;  oldrand[55] = random_seed;  new_random  = RANCONST;  prev_random = random_seed;  for (j1=1;j1<=54;j1++){    ii = (21*j1) % 55;    oldrand[ii] = new_random;    new_random  = prev_random - new_random;    if (new_random < 0.0){      new_random += 1.0;    }    prev_random = oldrand[ii];  }  advance_random();  advance_random();  advance_random();  jrand = 0;}double f_random(){/* Fetch a single random number between 0.0 and 1.0 - Substractive Method    See Knuth, D. (1969), v.2 for details */  jrand++;  if (jrand > 55){    jrand = 1;    advance_random();  }  return (oldrand[jrand]);}void randomize()  /* Get seed number for random and start it up */{  printf("Enter seed random number (0.0..1.0) > ");   scanf("%lf",&randomseed);  while ( randomseed < 0.0 || randomseed > 1.0){    printf("ERROR: Enter seed random number again (0.0..1.0) > ");    scanf("%lf\n",&randomseed);  }  warmup_random(randomseed);}int flip(prob)double prob;{/* Flip a biased coin...true if heads */if (prob == 1.0)   return 1;else   return (f_random() <= prob);}int rnd(low,high)int low,high;{ /* pick a random int between low and high */double fr;int i;fr = f_random();if(low >= high) {  i = low;} else {  i = ((int)(fr * (double)(high - low + 1)) + low);  if (i > high) i = high;}return i;}