#include	<stdlib.h>
#include 	<stdio.h>
#include	<math.h>
#include	<time.h>

#define	MAXTIME 	(500)
#define	NPATCH		(3)
#define ALPHA		0.05
#define	KK			1.0
#define CONFRAC		0.1
#define	MOVECOST	0.1
#define	TIMECOST	0.01
#define STAYTIME	(10)

struct patch_def
{
	double	k;
	double	alpha;
	double	size;
} patches[NPATCH];

struct con_def
{
	double	beta;
	int	staytime;
	struct patch_def *patch;
	double	time;
	double	lunch;
	double	inrate;
} consumer;

void InitSeed(void);
void InitCon(struct con_def *);
void InitPatch(struct patch_def *);
void GrowPatch(struct patch_def *);
void Feed(struct con_def *);
void Move(struct con_def *);

int main(void)
{
	int	ipat, ttt;

	InitSeed();
	InitCon(&consumer);
	for(ipat=0;ipat<NPATCH;ipat++)
		InitPatch(&patches[ipat]);

	for(ttt=1;ttt<=MAXTIME;ttt++)
	{
		for(ipat=0;ipat<NPATCH;ipat++)
			GrowPatch(&patches[ipat]);

		Feed(&consumer);
		Move(&consumer);

		printf(" %d ", ttt);
		for(ipat=0;ipat<NPATCH;ipat++)
			printf(" %f ",patches[ipat].size);
		printf(" %f \n", consumer.inrate);
	}
	return (0);
}

void InitSeed(void)
{
	int	seed;
	time_t	nowtime;
	struct	tm *preztime;

	time(&nowtime);
	preztime = localtime(&nowtime);
	seed = (int)((preztime->tm_sec+1)*(preztime->tm_min+1)*
		(preztime->tm_hour+1)*(preztime->tm_year)*(preztime->tm_year));
	if(seed%2==0) seed++;
	srand48(seed);
}

void InitCon(struct con_def *con)
{
	(*con).beta = CONFRAC;
	con->staytime = STAYTIME;
	con->patch = &patches[0];
	con->time = 0.0;
	con->lunch = -MOVECOST;
	con->inrate = 0.0;
}

void InitPatch(struct patch_def *pat)
{
	pat->k = KK;
	pat->alpha = ALPHA;
	pat->size = KK;
}

void GrowPatch(struct patch_def *pat)
{
	pat->size += pat->alpha * pat->size * (1.0-pat->size/pat->k);
	if(pat->size>pat->k) pat->size = pat->k;
}

void Feed(struct con_def *con)
{
	double eaten;
	eaten = con->beta * con->patch->size;
	con->patch->size -= eaten;
	con->lunch += eaten;
	con->time += 1.0;
}

void Move(struct con_def *con)
{
	if(con->time>=con->staytime)
	{
		con->lunch -= TIMECOST*con->time;
		con->inrate = con->lunch/con->time;
		con->time = 0.0; /* must appear here; misplaced in book */
		con->lunch = -MOVECOST;
		con->patch = &patches[(int)(drand48()*NPATCH)];
	}
}