coin toss problem

[celerysoup16]

I've written this coin toss program, and can't figure out why it isn't
giving accurate results...
cheers,
Ben

#include <stdlib.h>
#include <stdio.h>
#define H 1
#define T 0
#define SENTINEL -1

int count=0, seed=3645, limit=200, in_a_row=6, iterations=100;

void one_run(int seed_passed)
{
int i, x, row_h;
row_h = 0;

seed=(1+seed_passed);
srand(seed);

char A[limit+1];

for(i=0;i<limit;i++)
{
x=(int)(2.0*rand()/(1.0+RAND_MAX));

if(x==H)
A[i]=H;

else
A[i]=T;
}

A[i]=SENTINEL;

i=0;

while(A[i]!=SENTINEL)
{
while(A[i]==H)
{
i++;
row_h++;
}

if(row_h==in_a_row)
count++;

row_h=0;

if(A[i]!=SENTINEL)
i++;
}
}

int main(int argc, char **argv)
{
int i;
double av_occur;

if (argc==2)
seed=atoi(argv[1]);

printf("\nEnter number of coin tosses: ");
scanf("%d", &limit);

printf("\nEnter number of heads to be found in a row: ");
scanf("%d", &in_a_row);

if(limit<=1000)
iterations=100000;

for(i=1;i<=iterations;i++)
{
one_run(seed);
}

(av_occur=1.0*count/iterations);

printf("\nIf a coin is flipped %d times:\n", limit);
printf("Average no. of occurances of %d heads in a row is %.5f"
, in_a_row, av_occur);
printf("\n(with %d tests)", iterations);

/* printf("\ncount is %d", count);
*/
return 0;
}

[Richard Heathfield]

Old Wolf said:

Whether or not constraint violations are UB is a bit of an
academic matter (half the NG seems to think they are and
half think they aren't).

I don't think it matters either way, provided they continue to be regarded
as show-stoppers.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

[Richard Heathfield]

osmium said:

"osmium" writes:

Here's another cut at it.

I see the copy I posted is where I was fooling around trying to see how
many
trials it took to get a result of 1.0 It is in the vicinity of 128
trials.
Change the 128 to 200 to customize this to your question. Also note this
was compiled on a compiler that accepts some C99 syntax, E.g., \\
comments.

\\ comments? :-)

Incidentally, I am wary of a comment syntax that breaks when the text is
re-flowed, and which in any case constitutes a syntax error in a great many
extant implementations.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

[Mark McIntyre]

On Mon, 19 Jun 2006 06:09:14 +0000, in comp.lang.c , Richard
Heathfield <in*****@invalid.invalid> wrote:

osmium said:

was compiled on a compiler that accepts some C99 syntax, E.g., \\
comments.

\\ comments? :-)

for writing C in Arabic, of course.

gd&r
--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan