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> everytime the loop or the if...then statement populate myarray I
> use counter = counter + 1 to prepare it for the next value.
>
> can some one tell me what's wrong with this code?
That's a little hard because you didn't say what happens. But I
would guess you keep incrementing counter = counter + 1 -- even when
you've already put 10 values in the array. (Or 11, if you prefer,
since myarray[10] goes from element 0 to 10. But I'll assume you're
only using positions 0 through 9.)
If you keep incrementing counter, then the line that copies the last
two values to positions 0 and 1 will try to access past the end of
the array.
You will have to detect if counter is already 10 before you try to
increment it and, if so, shift all the values by one to make room.
I.e. put 1 into 0, 2 into 1, ... 10 into 9, and then insert your new
value into position 9. And don't let the counter get greater than 10.
You could also use what's called a "circular array," where instead of
shifting values when the array is full, you wrap around to the
beginning. I.e. fill element 0, 1, 2, .... 8, 9, then 0, 1, 2, ...
When you wrap around and insert a new value in 0, then your new 10-
long array starts in element 1. When you insert another value in
position 1, the array starts at position 2. Use a "modulo" function
to wrap your index into the array:
myarray[mod(counter, 10)] = NewValue;
counter = counter + 1;
Then you just have to make sure your "virtual array" starts in the
right place. You have inserted "counter" values in it, but there are
no more than 10 values in it now. The starting point of the array is
at myarray[mod(counter+9, 10)]. (That assumes counter is 0 before
you insert any values, then you insert them as shown above. The
first value is in position 0.)
Usually the circular array is used when you have a much longer array,
and shifting it is too expensive. With a short array like yours,
it's probably a lot simpler to just shift it.
Gary
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