Hacker News Reader

Comment by pascal_cuoq | Hacker News Reader

I do not know this language (Java?), but doesn't the line

   int offset = (int) (((size - 1) * ((long) key - min)) / (max - min));

compute (max - min) as an int (potentially overflowing), and then convert it to long, defeating the precautions obviously taken against this kind of event with the cast to long elsewhere?

View on HN

Let me try to break it down:

  (max - min) is int
  ((long) key - min) is long
  long / int is long since a long is involved.
  (size - 1) is int
  int * long is long

I think the purpose if the long cast is that the last multiplication produces a long and it doesn't overflow. But then it is casted to an int anyway defeating the purpose.

> (max - min) is int

Incorrect. These are signed values. If you subtract a large negative integer from a large positive integer, the result is larger than an integer.

Reply on news.ycombinator.com